It likely refers to the MODAP (MODified APollo) aka Apollo Logistics module.
This was a proposal for modifying the Command Module to support six crewpersons and adding cargo space to the Service Module (by downsizing the SM power and propulsion systems).
The MODAP CSM would have a stripped-down SM and a beefed-up CM. Because it would spend a limited amount of time in free flight before it docked with an Earth-orbiting station, the MODAP SM could dispense with or minimize many Apollo lunar SM systems. Batteries would replace fuel cells, for example, and a compact LEM descent engine could replace the SPS. The LEM engine would draw its propellants from a pair of spherical tanks in the MODAP SM's central cylindrical compartment. These deletions and additions would free up four of the MODAP SM's triangular bays for cargo transport.
...a 24-man space station with full crew rotation every six months would need to receive a MODAP CSM bearing six astronauts and 5855 pounds of cargo ...
- CM = Command Module
- CSM = Command and Service Module
- LEM = Lunar Excursion Module
- SM = Service Module
- SPS = Service Propulsion System
Details here https://www.wired.com/2012/04/apollo-space-freighter-1963/
There's an extremely similar article by the same author here http://spaceflighthistory.blogspot.com/2015/11/space-station-resupply-1963-plan-to.html which includes a schematic drawing of the capsule.
Quoted material comes from both articles - there is a lot of overlap, but the one at the 2nd link seems more to the point.