@James
Thank you for all of that information! I had no idea that this would be a regulated thing with requirements.

Another alternative is to stamp them on the metal ends of the tube, or metal base of the bulb. I have seen laser etched labels on lamp bases as well. Well hopefully modern etches hold up well.

The effect is extremely significant.  The luminous efficacy of an HPS lamp is determined in great measure by the amalgam temperature, which is typically set to deliver a D-line spacing of about 100 angstroms (or 120Å for the Gro-Lux types).  Higher sodium vapour pressure results in more light being wasted in the infrared, and decreased efficacy.  To measure this effect in the lab while holding all other parameters constant, we used to take simple MR16 halogen lamps and shine them onto the arc tube end where the amalgam is located, to cause modest extra heating.  Even a change of 10-20°C can drastically affect efficacy.  Hence the importance of keeping lamp dimensions and the amalgam dose weight and position absolutely consistent to avoid lamp-to-lamp variation.

In the early days when this was being investigated, and before MR16 lamps had become popular, manufacturers used to wind a small tungsten filament around the arc tube ends and provide the current to those via an extra seal in the outer bulb.  Very little heating was required to change the properties, and enable the optimum temperature to be set and recorded by pyrometry, and then tweak the lamp design until it self-heated to that point.  I do still have an example of an old 1960s HPS lamp with these end heaters.

A similar effect can of course be seen as the lamp ages - one of the primary mechanisms for voltage rise in HPS lamps (which limits their life) is the rate of end blackening around the electrodes. 

For your purposes, these effects may be small enough to live with, but it would not be a good idea for a commercial product.  Even for standard HPS lamps, the lamp and luminaire standards require that when an HPS lamp is installed in a reflector, the light reflection pattern has to be optimised such that as little light as possible is reflected back onto the end seals, and that the voltage rise of the lamp in the reflector should not exceed 5V.  Otherwise the reduction of lamp life in the fixture would be much too significant.

 Your biggest issue would be to find someone close to you as shipping would be rediculously EXPENSIVE !!!

As far as I know lanthanated tungsten was not used in HID electrodes.  As you say the efficacy is slightly lower, but we also found that we could see traces of lanthanum in the lamp spectrum.  Most lamps stayed with 2-3% thorium oxide right to the end.

What was used very widely was lanthanated molybdenum in wire and foils for HID lamps.  This showed significantly improved corrosion resistance and recrystallisation temperature, which extended the life of metal halide lamps.  It could not be used everywhere though.  I remember a big disaster when we changed to MoLa wire for the ignition antennas of HPS lamps.  It was found after some years that it suffered greater photoemission than plain Mo wire, and caused accelerated sodium loss and hence reduced life.  It was necessary to go back to pure Mo wire again.

In fact, the reason they were called etches is really because the ink was physically etched into the glass surface.  Unfortunately though the process is quite critical, and very often not done well.

The ink itself is a highly complex material uniquely prepared by the lamp industry, via an elegant chemical process that takes about 2 weeks to complete.  It basically involves dissolving the oxides of silver, lead and sometimes also copper into an organic syrup, laced with boric acid, which has the most wonderful smell you never forget after you have been in any lamp plant.  The ink is applied to the glass via conventional rubber stamping methods, and then burned in with a gas flame.  That is the critical part.  The temperature has to be high enough that the glass becomes soft, and triggers a reaction in which the lead borate chemically etches its surface, and draws the silver and/or copper ions below the surface of the glass.  The problem is that slightly excessive heating will cause the glass to deform.  It is very difficult to find the right balance, because there can be variations of one or two tenths of a millimetre in glass wall thicknesses from one bulb to the next, and the thinner bulbs are prone to deformation.  To avoid that, most setters of the Sealex machines err on the side of caution, and tend not to set the etching fires quite hot enough.  The result is that the etching reaction does not proceed fully, and the ink sometimes be rubbed away.

Many years ago this reached such a problem that too many lamps were losing their etches, which was considered a safety issue because the customer might not be able to read the wattage and know if they were installing a lamp within the the power rating of their fixtures.  The various standardising bodies such as the IEC and ANSI then developed a mandatory test for the robustness of the etch, which was taken into the IEC 61 standard for incandescent lamps and to this day has been copied over to most other lamp standards.  In the factory we have to take a soft cloth, soak it with hexane (a solvent for the ink syrup), and rub the etch softly for 15 seconds.  After testing it must still be visible.  I do think that since the 1970s most lamps probably meet this requirement, but of course we all know several exceptions where it has not been etched firmly enough.

GE lamps were another matter.  Some time ago they tried to shift to different ink types as a way of getting rid of the lead content, for employee safety reasons in handling the lead borate marking paste.  They developed a black air-drying ink based on copper oxide which did not have to be burned into the glass.  Some years later Philips also developed an air-drying ink with a golden appearance, which was rather better.  And Sylvania developed red colour inks which were extremely robust, but contained cadmium borate which also had to be dropped after a few years due to the environmental restrictions.

The reason internal etches was dropped was quite simple, because it was found that they can cause chemical contamination of the lamp atmosphere and lead to reduced life.

The problem with the glass frit decals is the same as the etch materials - they require high temperature firing.  That is fine for heavy-walled borosilicate lab glassware, but very difficult to control for 0.5mm thick soda-lime glass bulbs and tubes.  Also the speed of applying the decals is too slow and not really compatible with high speed automated production. 

@Multisubject — do you want a NORMAL MH400?

My biggest peeve is bad lighting. Ie, half-assed, poorly-maintained lighting installs. I have somewhat of a "perfectionist" nature, so if something like a chandelier has 16 different kinds of bulbs and three color temperatures, I will not be able to focus on anything else in the room, no matter how "nice" it may be.

Also flickering LEDs are up there. Recent-manufacture lamps from the likes of K-Lite (branded Philips) have a tendency to flicker horribly for no particular reason. They are straight junk in every application, and not worth more than $1/lamp, "unique" attributes aside (ie, SceneSwitch).

I also can't stand missouts. Like you went out of your way to replace every light in town. So WHY is there a light smack in the middle of it all, that is probably EOL, that is still in place??? My only exception to this rule is when a light left lit is something like a vintage MV lamp (ie, a local town converted entirely to LED, and they missed a Westinghouse OV-15 that's been reliably lighting dusk to dawn for the past 25 or so years).

There are more, but that's all I can think of so far.

 I've seen missouts here which were caused by blocked access to said fixture during the changeout process .

@James — Thank you! Interesting to see their company philosophy compared to a company like GE who built their factories in somewhat larger towns, and thus built them to a larger scale. In my opinion, from the 1970s onward, I would say GTE had the better finished product. Lamps made in Ravenna, OH, were DECENT, but had nothing on Sylvania's Manchester, NH-made lamps. And I assume different parts of each lamp were made in different places? And did Sylvania make their bases in house, or source from someone like GE?

@Ash: Isn't the CRI of SOX lamps Ra-44?

I had a Ledvance A60 13W 6500K snow cone LED lamp that lasted exactly 1 year of almost 24/7 operation at base-up burning: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-252219

I could go on but the list would be very long, there were well over 70 Sylvania and OsramSylvania factories in USA!  The main ones from most recent times have been named though.

Sylvania was unusual in that its management firmly believed in decentralisation of its operations, and avoidance of big cities wherever possible.  It quickly learned that employees were happier and delivered better work when they lived in the countryside, and were part of small communities where everyone knew everyone and showed better mutual respect.  Whenever a factory grew to a particular size, it was capped and they would open another factory elsewhere so as to maintain that small-world community spirit.

Big business owners frequently criticised this approach, claiming that bigger factories were more efficient - and indeed that may be true in terms of pure machine efficiency.  However, salaries are lower outside the big cities, and employees tended to stay longer on the job, allowing them to build up more experience and make better quality products.  Whereas the average seniority at many factories is only a few years before the workers leave and find something else nearby with better pay or conditions, Sylvania always enjoyed employee seniorities measured in the decades by treating its workers unusually well and ensuring that they had good lives in their local communities outside work, where substantial investments were made.  It had one of the biggest half-century clubs in the country, was one of the first companies in USA to introduce an employee health care program, and as such even today I know many colleagues who have clocked up 40 and even 50-year careers with Sylvania.  The company always found that despite the slightly lower efficacy of running multiple smaller plants, its total costs and quality were in fact better.  So much so that many management articles were written about this unusual approach, for instance the series "Big Business in Small Towns" that ran in Forbes, Time and Readers Digest - and whose popularity made even more people want to come and work for Sylvania.

Another cause was Sylvania's monstrously huge and fast expansion during WW2, which suddenly gave it a very large number of factories.  It's not well known that Sylvania was allocated the second most important project of WW2 after the atomic bomb, to develop and mass-produce a radio-controlled electronic bomb whose glass vacuum tubes were strong enough to survive being shot through the barrel of a gun.  These were manufactured in almost unimaginably vast quantities, over a million being turned out every 2.5 days.  More than 27,000 extra employees had to be taken on, and dozens of new plants were built, always in small communities, to produce the demands of the US and British armies for this top secret new weapon.  Just these 5 types of tubes made in the Sylvania factories accounted for more than 60% of the entire USA's industrial output of electronic radio tubes.  After the war, demand of course suddenly plummeted, and Sylvania was left with a lot of factories that would have had to be closed down - which greatly pained the company's founders since they had gone to such lengths to care for their workers.  So there followed an enormous expansion into the new areas of photoflash lamps, television, radar, photography, electronics, precision materials and atomic energy, as well as a massive push to build an export business that could keep people in work.  Of course not all of the plants survived, but most did, and most people could keep their jobs.

As such the list of Sylvania USA plants I am aware of are Altoona 1 & 2 PA, Bangor ME, Batavia NY, Bedford MA, Beverly MA, Bloomington, Brooklyn NY, Brookville PA, Buffalo NY, Burlington IO, Camillus NY, Central Falls RI, Cherry Hill MA, Cleveland OH, Clifton NJ, Danvers Hobart Street, Danvers Sylvan Street, Danvers Endicott Street, Dover, Dyerburg TN, Emporium PA, Exeter NH, Flushing NY, Fullerton CA, Gloucester MA, Hampton VA, Hicksville NY, Hillosboro NH, Huntington 1 & 2 WV, Ipsich MA, Jamestown, Johnstown, Kew Gardens NY, Kingston, Jackson MI, Lexington 1 & 2, Long Island NY, Lowell PA, Marietta, Manchester NH, Middleton MA, Mill Hall 1 PA, Montoursville PA, Mountain View CA, Muncy PA, Nelsonville, Ottawa OH, Point Pleasant, Reidsville NC, Riverside CA, Salem MA Boston Street, Salem MA Loring Avenue, Seneca Falls NY, Shawnee OK, Smithfield NC, Stamford CT, Standish ME, St.Marys PA, Towanda PA, Titusville, Versailles KY, Wakefield, Waldoboro ME, Waltham MA, Warren 1 & 2 PA, Watertown CT, Wellsboro PA, West Seneca NY, Wheeling WV, Williamsport PA, Williamsville NC, Winchester KY, Woburn MA, York PA.  It was a similar story in other countries around the world, once international exports really took off during the 1950s and 60s and required the construction of overseas factories - again according to the company policy, always in small towns.