Requires professional appraisal.
Never made by S&W
10-50 USD or so
Blue Book of Gun Values, on line auctions.
Derringer 2 Shot, 357 Mag, SN 929, what is the value
Which a single shot mississippi, split breach, vest, double derringer (model 95), caliber, variation? I'm suspecting your talking a double derringer 41 rimfire but that's likely not even a serial but a batch number. There's over a dozen variations with a HUGE range in value and even that's greatly dependent on condition.
20-50 USD or so
What is the value of a Davis Derringer pistol magnum 2 shot?
Impossible to answer. Requires hands on appraisal