See how much easier a number or two makes things?
Your Ted Williams is a Hi Standard Model 75, just about identical to the Supermatic model. Here is a parts list: http://www.histandard.info/manuals/hsashotguns/1167D150R.pdf
Sold by Sears from 1964-1968. 583.7500 is NOT a serial number, but the Sears Model number (there is actual a code to reading those numbers if you are a big fan of Sears marked guns) MOST Sears shotguns did not wear a serial number until the 1968 Gun Control Act required it.
Back to your fail to feed problem- difficult to diagnose at long range, but could be: (1) dirty gun- so if you have not, get a can of gunscrubber spray, flush the action area good, and light lube. OR- (2) problem with the cartridge stop (thing that keeps the shells in the magazine until they are supposed to come out) Could be stuck, broken, or loose. Time for a trip to the gunsmith. A FEW semi autos have a lever on the LEFT side of the reciever that keeps a shell in mag from feeding into the chamber- called a cutoff. Turned one way, shells feed, turned the other, they dont. Yours may not have one- but take a look.