More research needs to be done on the production. If you have 66 Nikon F, please email me the serial number. The F was produced several years after the introduction of the F2. In the late 73 range, F cosmetics were upgraded to match those of the new F2, including F2 styled plastic tipped winding levers, plastic tipped self timer, and threaded PC outlets. Again, production does not seem to be continuous.
More research needs to be done on the production.
These pics show the plastic tipped self timer and advance levers. US Military F's were made for the US Navy KS-80A, USAF, and Marines. Special Mirror F Lock up models appear in several variations. Most were manufactured by Nikon for the superlative American Mirror Lens manufacturer Q uestar. Others were modified by independent repairmen or perhaps by Questar.