Fatboy arrived today. In better condition than I was expecting, cleaned up pretty well.
Not NOS or mint, but definitely usable, tomorrow.
The yellow appearance is the lighting, not the brass (or gold). I checked with a loupe like his --->

4th quarter 1960 F 4 date code, crimped end cap in base of handle. Lucky it doesn't need disassembly.
Hopefully the detergent concentrate / bi-carb bath scrub and ultrasonic baths got all the cootees and soap scum out from inside the handle.
Pretty happy to add to this to my growing razor collection.