196x Roosevelt Dime, Error?

When I first noticed this dime it looked well worn. I cannot make out the last digit of the date, most likely 8, 9 or 0. I used a 7x magnifier on it thinking perhaps someone had sandblasted it as the wear was very even and not typical like on the 1954 Roosevelt reverse pic I uploaded. The obverse/reverse is not smooth, almost reticulated in appearance. I looked at the reverse side, it shows the same characteristics, I doubt someone purposely altered it so perfectly.

I then noticed the edge (reeding) was not even, a bit sunken rather than rounded. I measured it next to another dime and this one is a bit thinner. The height is visably shorter than other dimes. Don't have an accurate scale to weigh it but it has to be lighter than the standard weight, there's less material.

Does anyone know what happened to this dime? I uploaded an obverse, reverse and a side view (plus a 1954 reverse to show normal wear).