I'm new to the insulator world, and just starting to get a handle on glass. These 4 insulators came in a group of glass I got at an auction, and I was wondering if someone could tell me the U number and an idea on age. The one on the left has Pinco-G inprinted on it, the next has W underline in a circle, the next is not marked, and the last has something I can't read but appears to end in MAX or something.

Thanks!

Steve Lohr provided some good info, thanks!