Question re: S/N on Grips

[wreckville]

1 panel matches the Frame,the other has only J stamped into it.
I assume (knowing what that can mean) the latter is a replacement panel?

 

[arjay]

Normally just the right panel has the serial number

 

[JSR III]

What is the gun?

 

[wreckville]

M37, 3" ,floating J s/n.

 

[wreckville]

Thanks for replies folks. Most appreciated!