"Non-fill" refers to a pressing defect that occurs when the molten vinyl does not flow fully to produce a well-formed groove. It occurs most often on a 180g record's outer edge and is caused by the vinyl's beginning to harden prematurely.
You say you don't want to spend hundreds on an original LSC-1806 "Living Stereo" or LSC-1817 or $1500 on the Soria box set LDS-6065? That's understandable. By the numbers: LSC-1806 is the 1954 stereo spectacular "Also Sprach Zarathustra" with Fritz Reiner conducting the Chicago Symphony. Of course RCA couldn't issue it on vinyl in 1954, though it did issue it in stereo on reel to reel tape well before the vinyl, which didn't get released until 1960.
Do you own a copy of Buckingham Nicks? It was Stevi Nicks and Lindsay Buckingham's pre-Fleetwood Mac pairing featuring an icky cover both probably regret. Issued on Polydor in 1973 it's credits show that the duo and producer/engineer Keith Olsen knew what they were doing!