As long as there is no ‘grease’ on the back I would leave it alone. If any grease the clear won’t stick to that area. I have carefully cleaned BG’s with a lightly dampened paper towel using Windex. Proceed w/caution if trying.

I've usually regretted cleaning attempts on a flaking backglass. They are just simply too fragile in that state.

If an area really needs attention, a damp q-tip will offer a bit more control than a cloth.

It's usually better just to leave it alone and seal it as-is. Unless it's really bad, the grime doesn't really show through on the front. Your glass looks fine, for the most part.

100% agree with previous two posts - leave it as is (and it looks pretty good as-is btw - your flaking is minor). Not worth even the minor damage you can do wiping it down. You will kick yourself 1 second after you see even 1 flake come off.

For cleaning it, less is more approach.

Ps - if you are taping over the score and credit windows before sealing, make sure that tape doesn't touch the edge of the ink as it will want to take it with when you go to remove the tape after sealing. Ideally, you want a tiny bit of clear to enter the score window edge to seal the ink around it.

On solid state games, I haven't bothered with masking the windows. Just put down thick coats on the windows, and they turn clear. Any issues, and I just take some novus 2 or 3 to it.

I'm not sure how that would look on the white reels of an EM, though. The triple thick doesn't always come out perfectly level, which doesn't matter a whole lot for lit displays that mostly have dark areas.

I have usually just sprayed the TT over the openings for the score reels. It is only really noticeable that the TT is there if you look very closely at it. When standing in front of the game one would have a very hard time seeing the TT layer. This also locks on the white colour around the openings.

Business cards might not be thick enough or heavy enough. You may get some seepage under the cards.

Personally, I stopped doing the masking approach because it took longer to prep, you could see the edges of the triple thick in the score window, and it sometimes left ink exposed to possibly flake away later.

I just cut out a few blocks of wood and set them down on the windows. Never had a problem.