RE: Orbit single stick radios
The servos with the older open stick radio are PS-2, the one with the newer Orbit are PS-4.
PS-2 servos were available in both analog and digital form, while the PS-1 servos were only analog. On the lower right of the front plate is "4-8 D Proportional", so it does look to be an early 4 channel digital Orbit.
At one time the Orbit PS-2 was THE servo mechanics, with Orbit, Micro-Avonics, EK, Kraft all using it as well as a bunch of smaller companies. Even Sterling used it in their command master.