All Colt revolvers have factory inspection stamps.
The standards are a letter stamp on the left rear of the trigger guard which is assumed to be the assemblers stamp.
The tiny "VP" in a triangle on the left front trigger guard is Colt's Verified Proof stamp, verifying that the gun passed it's proof test.
There will be at least one letter stamp under the serial number on the frame. This is assumed to be the final inspectors stamp.
You will also see various inspection stamps on the left side of the grip frame under the grips.