Oh well, I was hoping to give you an exact maker.
Anyhow, the gun is not a Smith & Wesson it is one of the jillion or so Spanish copies made from the early 1900's up until World War II or so. S&W never serialized like that, nor marked the frame in that way.
Many different small gunmakers in the Eibar region of Spain made copies of S&W Military & Police revolvers, as well as Colt Police Positive copies, for sale domestically and for the South American market. The 'SPAIN' marking on yours could indicate it was specifically exported to the US for sale.
Value is uniformly low, and depends completely upon whether the gun is safe to shoot. Many were marginal when new. Certainly no more than $125 or so and more likely less than $100.
The autonomic nervous system provides for involuntary muscle function - the work of breathing, digestion, and so forth. On some folks, that's a pure waste of ingenuity.