As with any firearm, it is not possible to accurately appraise a gun without seeing it. Condition, and original configuration will determine value. Other factors such as rarity of caliber or guage and higher grades have significant impact on value. Recommend that you see a local gun dealer for an 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.
Impossible to answer without a detalied description of all markings and features.
No such animal......
Browning never made a Model 51 shotgun.
Which model?
It's the model code for a 12 gauge Magnum.
What model of browning shotgun are we talking about? I would need to know this in order to help you answer this question.
$1,000 to $1,200
No
You will have to call Browning to find out.
What model?
50-1000 usd
Can't answer about "Volunteer" question. Please tell which model. Volunteer is not a model by Browning