A sadly tiny illustration of a “Saturn Space Laboratory” from a circa 1960 NASA brochure (promoting the organization to college students). This looks like something halfway between MOL and Skylab; three pressurized modules in a “wet lab” space station. Diameter looks to be 10 feet, same as the Titan booster; early concepts for the Saturn called for the use of the Titan first stage to be the second stage of the Saturn I, with the second stage of the Titan being the third stage of the Saturn. This may well represent a Titan I or II first stage/Saturn I second stage as a space lab.
Given the entertainingly toxic nature of the Titan II propellants, I’d guess this was an earlier Titan I-based concept.