Hello everyone !!
do you have any informations about NITRA and AZO osram light bulbs ??
 which is the oldest ??
thank you in advance for your help !!   
   

Hi .  honestly osram azo is older than osram nitra.  osram azo i think it starts around 1910.  ends in about 1919.  The funny thing is that I have seen osram azo without an exhaust point, therefore about 1920 it could have ended.  Another detail is that there is an osram nitra with a tip exhaust.  then before 1920.  it is very difficult to know exactly but osram azo ended around 1920.  and osram nitra ends in 1940.  there is osram nitra with exhaust and osram azo with exhaust in the tip both. it could be that some factories exceeded the manufacture until they end stocks and then move to nitra.  it is very difficult to really know the story.  My conclusion is what I have seen, I hope to help you, greeting

As far as I know, both were used in parallel but in different countries.  After the start of WW1 Osram lost many of its divisions outside Germany, which were naturally confiscated by the local governments.  These divisions were sold by the state to new owners, who were given automatic rights to the Osram brand in those countries. There was then a complex situation where there were many different Osram companies. 

In the following decades after the war, the original Osram German company was still forbidden from exporting its lamps in many countries, because it no longer owned the rights to its brand name, and was not allowed to compete against the national divisions it had lost.

The same situation applied in some cases to sub-brands like  Nitra and Azo.

It us my understanding that the original German gas-filled lamps were introduced a year before WW1 under the Nitra name.  After the war, in some countries the Nitra brand remained with Osram, and in others it had been transferred to the new owners.  I believe the Azo name was introduced only in French / Italian / Spanish speaking countries to get around this.  It is short for Azote/Azota, in the same way that Nitra was short for Nitrogen.  I don’t know who had the rights to it though.  Maybe it was Osram Germany who was forced to produce under that name if it wanted to sell to France be because the competing Osram-France too ownership of the original Nitra brand, or maybe it was the other way around.

It took a long time for this mess to be cleared up.  In the 1920s-30s-40s Osram Germany gradually rebuilt itself from near total destruction, and became rich enough to buy back a few of its foreign operations.  France was one of the first countries to be taken over.  But then with the start of WW2 that investment was wasted.  The foreign divisions were confiscated again, and then the old brands had to be resurrected.  It was not until 1990 that Osram Germany grew strong enough to buy back the last of its overseas divisions.  Incredible that it took that company 76 years to recover from the damage done to its international operations by the two wars!