I happened across this piece in a local antique shop. It's from 1980 and is really grungy. It looks like someone put some tape on it and also tried to clean it. But I figure if I let it sit for a few decades, it will develop a good patina.
The back is fairly non-descript. This is a design I've seen on some other bars from different companies, but all minted by Pioneer Mint.
This is the kind of stuff I always keep my eyes out for.