Wow, there's some real confusion here! The A06B-0373 shows up in my cross reference as a 1-0SP/3000 motor. The A06B-0123 does cross reference to an Alpha 3/3000, so that one checks out.
(A quick look at labels on eBay confirms that there are two "models" with the same "part #". I had no idea that Fanuc ever did this.
The specs on the motors look about the same, though.)
Anyway, the last 2 digits are the encoder type, and 75 means an A64 serial pulse coder. This gives 65,536 counts/revolution, and produces low-res absolute data immediately on power-up, so you don't need battery backup to have commutation data for the motor.
So, the Pico Systems serial Fanuc converter is suitable for these motors.
Jon