Hello to all! I am new to the forum. So thanks in advance for bearing with me while I figure this out. Really need some help trying to figure out this Smith and Wesson model 10. From what I can gather from the serial number it's was manufactured in 1960 .. but what stumps me its the "extra stamped serial number" pictured below the cylinder on the left side. Could this be an old police or military duty revolver the issued there own serial numbers. I have came across a lot of model 10s and pre but never came across anything like this. Any information on this would be helpful.

Thanks in advance! Andrew