We would need to know the model number and other specifications to possibly answer your question. As with any firearm, it is not possible to accurately appraise a gun without seeing it. 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.
According to www.gunbroker.com and other dealers, if it is in good condition it is worth around $360-$400.
50-300 usd
50-375 usd
50-225 usd
The Buckmark is a newer version of the same design. Challengers came in 3 models or versions (I, II, III), each being made after the former was discontinued. The Challenger III was very very close to the current Buckmark design, with the aluminum frame in common with the Buckmark. Challenger I and II both had steel frames.
100-500 USD
50-500 uSD
You will have to call Browning.
there is a dedicated web site for browning auto 5 shotguns, google it.
50-500 usd
50-500 usd
50-5000 USD depending on specifics.