It's a model 36 (J frame). They came with round and square grip frames.The serial number is: J26XXXX
It has the handle of the Model 10-5 but the body of the air weight Model 37, but I can't seem to find a model that has both of those
Serial numbers ran fron J250001 in 1975 to J370000 in 1976.
A model 36 is the all steel version of a model 37.
If you open the cylinder you will see the model number stamped on the frame cutout forward of the cylinder.
Jim