Revolver identification and serial number location

[Etraveller]

I was looking at a revolver, and was trying to identify the possible manufacturer.
The revolver resembles a S&W military and police revolver in most if not all aspects.
On the right side of the barrel was stamped: Made in U.S.A.
The barrel was tapered, and on the underside, was stamped i believe a six or seven digit number, and this same number was stamped on the rear of the cylinder (closest to breechface).
the number 59990 or something similar was stamped on the inside of the yoke, and on the frame opposite the inner yoke, but I believe this to be the part number.
There appeared to be no stamped markings on the butt of the pistol.
When I get a chance to check the rifling, I'll be able to eliminate if it is not a S&W military and police.
Any suggestions as to the correct position of the serial number and a possible manufacturer of the revolver?

 

[Sir William]

Three possibilities. First is that the numbers you see are assembly number stampings and it might be a Model of 1905, 1st-4th change S&W revolver. Second thought is that it is a S&W M&P revolver and the assembly number stampings are still properly located. The S/N should be on the butt unless there is a lanyard ring. The S/N would then usually be moved to the bottom of the barrel, the front of the gripframe, the cylinder chamberface, the hammer and in many cases simply every part is S/Nd. The third idea is that the revolver could be a very close copy of a S&W from Belgium or the Eibar region of Spain. Somebody with the SCS&W will be along to interpret the numbers soon. A pic would help. Are there two maltese crosses with patent dates on top of the barrel? If not, it likely is a S&W M&P. What type of trigger does it have?