Stevens 58AB

Hello, Yesterday bought a single shot 12 ga at work unseen. Turns out the gun is a Stevens model 58AB in .410 any thoughts where I can get info on this?? mainly what the letters following the 58 which in this case is the A and B ?? and as you can see the guy I bought it from doesn't know didly about guns !!

The A and B are series changes, most likely the switch of a small part that was screwing up alot.

Can you find a date code on it anywhere? Small oval with a letter and number in it.