Ex DC10 driver here...I can shed some light on this.
These units were indeed DC10 fit
The first unit is the Litton 72. From memory only 9 waypoints could be entered in sequence, all using Lat and Long co-ordinates.
The second unit is the Litton 92 which had a database containing user waypoints which saved entering Lat and Long co-ordinates.
I think the 92 had 100 waypoints that could be strung together simultaneously to create your route.
I have both these units on my shelf and used both during my years flying the DC10 itself.
Waypoints were entered on one unit only whilst the other two were set to ‘slave’ or RMT. The waypoints would then automatically be transferred into the two ‘slave’ units and after completion of data entry all three units were placed into AUTO and made their own calculations as to their position. This would in turn provide the triple mix position to the Navigation system and reduce position error. Radio updates from DME/DME would periodically bring about a course correction. When flying trans Atlantic and passing Lajes, the aircraft would get a radio update and would usually turn slightly to put itself back into the exact position.
Accuracy of the units was pretty good. Usually less than about 0.3nm/hour of operation from what I can remember.
Like all INS systems, POS INIT at the start of the flight was quite critical as getting it wrong on the ground meant the boxes couldn’t be re-initiated once in flight.
I still have the user manuals for both these units from the manufacturer and the Lam Schematics for the aircraft fit.