Model 36 659XXX on the butt and 486XX stamped on the crane or yoke. Any idea whats going on, maybe cylinder and yoke/crane change? where could i find info or if you have it please share.

The number on the butt is the serial number. The number under the crane is simply a factory assembly number which matches a number inside the side plate, but has nothing to do with the SN. Assuming there's no missing letter in that SN, production date would be in the later 1960s.

HTH!

Steve