Jim,
If the cartridge is of the vintage I suspect, the model number is on the top of the cartridge and is visible only when removed from the headshell.
The Audio Technica cartridges are often private labled (i.e. the same cartridge will have many different model numbers so that it cannot be price shopped from store to store.) If the cartridge you have is a dual magnet model with a colored stylus assembly that mounts from the bottom, this is definitely the case. The styli are actually interchangeable and the level in the lineup is noted by color: red was low (conical if I remember correctly.) Green was higher, and ivory and orangy brown were above those. (The top styli often had a built in stylus guard and a Sibata tip.) The stylus can be removed by sliding up and backwards simultaneously, if you are looking down at the underside of the cartridge, with it removed from the arm. When it is seated in properly, it will "snap" into place.
These styli are common and plentiful: you shouldn't have a problem finding a replacement. Genuine AT styli have the AT logo on the plastic behind the cantilever. They were pretty good cartridges, with excellent seperation, due to AT's prorietary dual magnet design.
I hope this helps.
