Once upon a time there was only one Shimano chainring size standard, it was 110 mm for the big and middle ring and…. …. for the small ring (sorry I have forgotten).
The 110 and the xx mm standard was actually quite good but by reducing size of the chainrings both in the front and in the cassette it was possible to reduce weight of the drivetrain, but then you needed a smaller bolt circle than 110 mm.
This is a nice classic 110 mm 46 tooth Shimano SuperGlide big ring for a Deore XT (or DX) crankset.
Really nice finish on this one and because it is SuperGlide it is supposed to be easier to shift (I think, I have forgotten if it was specially shaped teeth on the chainring or something else, comment if you know the truth).
Slightly worn but still functional (and cool looking), it would look great on any vintage mountain bike and it is yours for only 15 euro.