ktrobins:
Terminology: Crane = Colt speak, Yoke = S&W speak. Its the bit that joins the cylinder to the frame.
The J & 17620 are assembly numbers, used to track fitted parts in the factory. They are not recorded and have no meaning after the gun is manufactured.
C272229 is the serial number. The C prefix indicates a fixed sight 'K' or medium frame revolver. In your case this is a Pre-Model 10, the .38 Military & Police Postwar, manufactured in 1953. Model numbers were not introduced until 1957, hence 'pre-model 10'. The Model 10 is still produced in a modified design.
There is a very slight chance that the gun is a pre-Model 12, the.38 Military & Police Airweight with an aluminum frame and cylinder. If so it is a) unsafe to shoot and b) a collectors item. S&W replaced the aluminum cylinder on the Airweight in 1954 due to cracking cylinders. Put a magnet on it. If it sticks its safe to fire with any current commercial .38 Special ammunition.