These two designs shared many of the same design elements.
Both models were short, had solar panel fins and used an existing NASA style capsule.
I always liked the Orbital Transport Laboratory designed by Ted Nomura (Shown at the upper left). It was the June 1971 winner of the Estes Design of the Month contest. The plans were printed up in the Estes Model Rocket News. The model was also seen on the cover of the 1972 Estes catalog. For the JimZ plans: CLICK HERE
On the right is the Apollo Earth Orbital Workshop designed by Ronnie Cramer. It was featured in the August 1971 issue of Model Rocketry Magazine; CLICK HERE
These two designs are enough alike that one probably inspired the other. Which came first?
Both the Estes MRN ad Model Rocket Magazines have dated covers, they didn't always arrive at your mailbox by the posted month. A June issue could arrive in mid July! These two designs were printed within two months of each other.
Magazine submissions rarely go into print the week they arrive at the publishers. Some articles will sit for months before being used.
Here's another Apollo Earth Orbital drawing from a later Ambroid glue ad.
I doubt Ronnie Cramer ever got residuals from Ambroid copying his design.
Centuri had a solar paneled kit, "Available February 1, 1972".
The Sky-Lab fins may have been spurred by these earlier designs.