Any utility grade single shotgun in working condition is worth about $50 - $75. Would need more information to determine the age - exactly how the J. Stevens company name is written will get us close. There's nothing unusual about a break open single shot having an open hammer if that's what you mean by "cock like a hand gun."
The owner's manual, configuration and comparison with known examples.
It a Savage models ... 30D, 30E, 30F or Stevens model 67
They came in various barrel lengths and choke combinations. If it is not marked on the side of the barrel, you will have to pattern the shotgun to determine the choke
No way of knowing without a serial number /model number to identify what type of .410 gauge stevens you have.
About $50-$75 as a mantle decoration.
Good shotgun
The AA-12 shotgun( Auto Assualt twelve) and the Mosberg shotgun.
It shouldn't say light twelve on the barrel, but on the receiver. Light twelve means that the gun is a light weight version of the standard Auto5 shotgun.
Your serial number indicates that your Browning light twelve auto-5 shotgun was made in the year 1955.
what do you want for it
100-500 usd
A shotgun in 12 gauge.