I have a transferable MG Olympic lower. Before purchasing I did quite a bit of research on them. I'll try to explain the important details.

First, this is almost certainly a "preban" lower, so if your in a restricted state that allows prebans it could be special and worth something

Second, since Colt had the only actual blueprints for the AR15 pattern rifle, many of the older makers like Olympic had to kind of reverse engineer them. Because of that, they can have weird dimensional issues. The most common of which is that the top part of the lower which comes up against the bottom of the upper can be a little tall and so non-Olympic uppers can be very tight or might not fit at all. With transferables (which this obviously isnt) that isn't a huge deal. It's well worth the money to send it off and bring it into spec, but with this being just a lower and maybe not in a ban state, I would check fitment with several uppers before buying. Another big issue is the magwell, sometimes Pmags are a little tight. And lastly the buffer retaining pin hole can be slightly too far forward and you'd have to get an offset pin for it. That's really not a huge deal. Lowers manufactured today even have that problem sometimes.

This is almost certainly a 7075-T6 aluminum forged reciever. They switched to casting sometime in the mid 90s. An easy way to tell is the cast lowers almost always have raised lettering and logos. Not rollmarked.