I bought a bunch of these at a salvage store a few years back. They are made in Mexico and are short A-21s (like a traffic signal bulb) with etched frost finish. They are unusual in that they have a very long luminesence (light up) and nigrescence (cool down) interval, almost like what you'd see with a 300 watt bulb. The bulbs also blacken a lot during normal use. They act like they would last forever. They have very yellow light output. I cannot find them in any Philips catalogs. They are in single sleeves and do not appear to be very old.

I will check my 1993 Philips catalog to see if this lamp was listed. These railway lamps are definitely pre 1999 because Philips changed to fake frost on almost all of the A shaped incandescents. They may be vacuum if they go on and off slowly. Again I will have to check. I will also check the 1983 Westinghouse catalog to see if this lamp is listed. I dont have a 56 watt lamp yet but I do have a 105 watt and a few 189-202 watt bulbs. The Philips date codes read like 8B or 1A, things like that. Please email me the date codes and I'll let you know. The date codes are right on the etches, should be easy to find.

The sleeve lists the bulb number as 56A21/BR 130V.  The bulb was made in Mexico and has the "starburst" soldered button on the base.  The crown of the bulbs says "Street Railway" and has "7D" as the only identifying number on the crown.
I was thinking it might be a vacuum bulb.  It does not act like any other extended service lamp I've come across.  The others that I have had in use darken a lot over time, if that has anything to do with the vacuum.

Yes as I have pointed out in my email, that the 56 watt street railway lamps are vacuum. Your lamps are from April 1997. I am just repeating this for the other viewers who may be reading this.