I want to give my 2 cents. I had seen quite many old refurbished thin sections, and I also had achieved that for one single thin section for my PhD (there was only thin section, no rock sample).
1. Tip for removing the cover glass (the easy step).
If the type of glue used for the cover glass is Canadian balsam it is very easy to get the glass dis-attached from the sample by freezing cycles (simple house freezer, I had done 8 cycles of freezing-unfreezing and the cover glass just completely got dis-attached.
2. refurbishing the thin section for modern EPMA (this is extremely difficult step, this requires very experienced grandmaster (we call them so) of thin section maker, luckily one of such grand-master is working in our institute).
The steps is quite clear:
2.1) very carefully removing the residual Canadian balsam from the fron side (where cover glass was removed) - the surface is very lightly polished
2.2) That polished side is glued with EPMA grade epoxy to the new base glass
2.3) The old base glass is little by little polished away to uncover the back surface
2.4) so if in last step glass had not split into pieces, or the sample was not too much polished away – You should have a new EPMA ready thin section . The difference from original is that it is mirrored – the back side of original thin section becomes new front side of the thin section.