Total width is 3 1/2\", to the outside of the frame. Both sides of the glass are convex, but one side is more domed than the other, the one that would be away from the lamp. I don\'t really know what this is for. It does make things look bigger. So, I thought maybe it is like what photographers use to view their pictures. But it says something about a lamp on the rim, so maybe it is for a projector? Not sure, hopefully you know. It has some wear, shown in the pictures, but the glass is not broken or chipped and it is not loose in the rim. The glass does need cleaning and it has some scratches, both of those shown in the last two pictures.

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