I'm looking at two M&P's. One is a 4" 5 screw and the other a 4screw 6". The serials on the cranes do not match the numbers on the bottom of the grips. Should they match, or do they mean something different?

The number on the yoke (crane) was a means to keep track of fitted parts during assembly; it should be stamped on the frame recess for the yoke and possibly elsewhere on the frame on a gun with matching parts. The letter(s)/number on the bottom of the grip frame is the official SN.

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Alan
SWCA LM 2023, SWHF 220

You don't need to give us the complete serial number for us to help you date the guns -- 5678xx will work, to make up an example, and get us close enough. Be sure to let us know any letter prefix to the serial number. You might see a V, S, C or D out there in front (and a K on target models), possibly separated from the numerical portion by several spaces. On prewar and some postwar revolvers you will also find that serial number stamped on the rear face of the cylinder and the flat underside of the barrel.

Pictures would help. There are some instructions elsewhere (FAQs and the forum office? You'll have to look for them) on adding images to your post.

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David Wilson

The official S&W serial number is on the butt. The numbers you are seeing in the yoke are assembly numbers.