OK, I just spent close to an hour taking pictures/talking on the phone with an FRRP tech. about the 4.10 gears I received from Late Model Restorations (LMR) in Texas. Here's the definitive word from FRRP on their USA-made 4.10 gear and pinion set:
(1) there is only ONE Ford 4.10 ring gear and pinion set made, NOT two (i.e., there is NOT an "OEM" set and a separate "Ford Racing Performance Parts" set with one being "non-forged" and the other "forged") ;
(2) the ONLY 4.10 ring gear and pinion set that Ford has EVER made in the USA (i.e., FRPP # M-4209-G410-A) has ALWAYS been made by Ford at its Sterling Axle Plant in Sterling Heights, MI, NOT by U.S Gear (historical note: Ford originally owned the plant, then Visteon took it over when it was "spun off" from Ford; now Ford has the plant back under its own name again);
(3) ANY and ALL 4.10 ring gear and pinion sets purchased at a Ford dealership and labeled M-4209-G410-A are domestically produced and are available through BOTH FRPP AND the dealerships- i.e., there is NO difference whatsoever between the two;
(4) any genuine USA-made 4.10 ring gear and pinion set made by Ford does NOT have the pinion depth marked on it- if it does, it's NOT made by Ford;
(5) not all genuine Ford ring gear and pinion sets have the Ford logo on them for reasons best known to Ford (probably a money-saver since the raised logo stamping costs money);
(6) ANY 4.10 ring gear and pinion set labeled M-4209-G410M ( not "A") is made for Ford by Motive Gear in Motive's Italian plant.
BTW, the ring gear and pinion set I received from LMR is the GENUINE USA-made FRPP 4.10 set that I ordered (at a GREAT price I might add).