The Colt .38 Police Positive was introduced in 1905. Over 200,000 were made before it was discontinued during WWII. The serial number would indicate the date of manufacture, but I can't read it in the blurry photo. The grips (if original) indicate production between 1909 and 1923. It is chambered for the .38 Colt New Police, which is identical to the .38 S&W (NOT .38 Special). Modern .38 S&W cartridges can be safely fired in that gun if it is otherwise in good condition. The term "positive" when applied to a Colt revolver indicates it has Colt's "positive" hammer block safety that does not depend on spring action.
Value, as best I can judge condition, would be around $200-250.
NOTE: ".38 Smith & Wesson" or ".38 S&W" is the name of the cartridge, and does not indicate the make of the gun itself.
Jim