Nice collection man. I found a all stainless steel model at the thirft store today all beat to hell something was wrong with the motor tho so i bought the small stainless mixing bowl it came with and left the mixer
The later models of this size went to electric. Heating defrost i belive after 65 or 66. The units with exposed coils just scream hot gas defrost by design. My guess whould be exposed coils=hot gas defrost
The hot gas bypass whould close way before it got too warm . I did the same thing when i first got my combo. Left the thermostat off and the inside got to 80 in my 65 degree basment. I felt the butter condisner and it was still giving off heat even with the thermostat off.