Need help identifying cartridge

Hello, I have what I think is a low-output MC cartridge circa approx. 1982. The body is rectangular and silver in color; appears to be made of either plastic or aluminum. The dimensions are approximately 1" x 1/2" x 5/16". The only marking is on the front of the cartridge, a logo which resembles a cursive small "s", with the last stroke going horizontally through the body. A small dot is above this horizontal line.

E-mail me if you want pictures. Thanks.