From what I see in most Quarters, especially of the 1980 range, is that the mint mark is always too small. I think its a typical mint mark, nothing special.
I don't collect a lot of quarters, but I do remember some of the dates - 1979 and 1981 - some of the coins can have a different variety of mint marks.
Whether those apply to quarters, I don't know.
The rim on the reverse is a tad thicker on the top of the coin than the bottom, but it looks like its well within tolerance, or considered a "normal coin".
Keep Digging ! Something will ring the bell sooner or later.