Ok, I got a couple of failed lamps from the library today and I need help with the date code.  The first lamp is a Philips 70w MH.  The code is M2-1.  The second lamp is a Sylvania 100w MH and the code is M90 R. 

Thanks for any help you can provide

Philips - Made in December 2002.
Sylvania - M90 is the ballast code. Try looking at the screw base.

Thanks for your reply to the Philips. I cannot see any other code on the Sylvania lamp, but near the base has turned that metallic silver color.  The etch on the lamp looks new, so I don't think this lamp is that old.