Date codes here could be a clue here. The left one may be June 2009 or September 2006 and the right one may be June 2007

Date codes here could be a clue here. The left one may be June 2009 or September 2006 and the right one may be June 2007

Does anyone know why the factories generally use strage codes instaed of just writing the date of production as it is. Markings such as "Made in Europe" were also not very helpful. Can't they be a bit more specific?

I don't know why they can't be more specific. If a code is printed on the bulb then it should be of some use to the consumer.
The filaments are different on these. The silica coated lamp has a European style filament, while the one on right has a wreath, more common with Chinese lamps