What revolver can it be similar to 1907 Colt Police positive But only stamped with 6 digit SN on grip bottom and 39 on several places?

The Spanish made good (and bad) copies of American design guns into the 1930's that often were not well marked. Look at the underside of the barrel for the word "EIBAR", which is the region of Spain where hundreds of little gunsmiths made firearms. Look also at the grips for a logo similar to a Smith & Wesson logo.