So most lamps have their date code on the stem press of the lamp itself. The problem is, on coated and frosted lamps it is impossible to see the code without breaking the lamp. Would it be possible to xray the lamp so that the code would be visible without breaking the lamp?

Very good question!  Just last week I had the same idea when trying to read the embossed date code in a GE reflector lamp.  I think the answer would probably be yes.  The glass in those older lamps used to contain about 20% or even 30% lead oxide by weight, which makes it an excellent absorber of X-rays.  I think if the accelerating voltage was set to at least 75kV it should be possible to penetrate the glass, and then any thickness variations should show up.  When I have a moment I will take a couple of these kind of lamps in to work and have a go on the X-Ray machine.

Very good question!  Just last week I had the same idea when trying to read the embossed date code in a GE reflector lamp.  I think the answer would probably be yes.  The glass in those older lamps used to contain about 20% or even 30% lead oxide by weight, which makes it an excellent absorber of X-rays.  I think if the accelerating voltage was set to at least 75kV it should be possible to penetrate the glass, and then any thickness variations should show up.  When I have a moment I will take a couple of these kind of lamps in to work and have a go on the X-Ray machine.

Nice! If you do go and xray some lamps, do try and post the images here! 

If the lamp lamp have a clear band around the cap, maybe try to illuminate the stem press with laser or with narrow beam of polarized light and see if any outline becomes visible ?

I have tried it out!  See images and results in the gallery photos here.

I have tried it out!  See images and results in the gallery photos here.

Cool!