Which model? Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. Condition and age is also a factor. Auto 5's with recoil pads (other than Mag 12's) poly-chokes and compensators will reduce value. Recommend taking it to a gun shop for appraisal.
You can also do your own investigation by looking at other models being sold that are in the same condition as yours. Try the gunbroker.com or a periodical called "The Gun List"
You can also reference the Blue Book of Gun Values which can be purchased on line at various retailers.
What is the value of a 12 gauge Browning shotgun serial J68824?
$350
1943 browning light 12 belguim made $5K
If you mean a Browning B-2000 12 gauge shotgun then the value would be 495 dollars for a shotgun in the condition you describe.
Basically impossible to value a weapon with just the gauge and sn.
Browning Citori 12 gage over and under & a Browning Goldtrigger Light Twelve: How much are they worth?
Browning never made a Model 51 shotgun.
The value of a 12 gauge Browning Citori Pigeon Grade is actually dependent upon a number of factors. Some of these factors would be the age and condition.
100-500 USD
50-500 usd
You will have to contact Browning.
0-400 usd