RCA, as much to my knowledge from having been a pre-recorded reel collector, always supplied their own tape stock under the branding "Red Seal". It was red acetate during the 2T era (1954-1959) and brown acetate in the early 4T era (1960-1964). Starting somewhere around 1965 (basing this on having Elvis tapes and The Sound of Music soundtrack), they changed to a rusty-orange color polyester; until Magtec became their duplicator in 1971 and used Scotch 203 formula with a dark grey oxide.
The Magtec 7 1/2 reels from the early '70s of Bowie's RCA albums are FANTASTIC (as well as their quad recordings by Ormandy and the Phila. Orchestra). However, the Scotch 203 formula IS prone to losing its lubrication and leaving your pinch roller chalky white(!). I once remember reading an archival Billboard article from 1972; where, a rep. from Magtec (at the time) was still committed to releasing consumer reel to reel as a format and: he'd said Magtec only duplicated their tapes at 4x the speed (vs. the way Ampex, usually, had duped them between 60 - 90ips). The WORST pre-recorded garbage, though, was Columbia House. THAT was a total insult to what consumer reel to reel was/is capable of. Columbia House duplicated at 130ips USING MASTERS EQ'D FOR *CASSETTE*.
Ampex (generally) used Ampex formula 642 brown polyester; however, when a Pop album tape was a big seller: a lot of reissues were made on Scotch 190 formula. There are often multiple copies of the same Ampex-manufactured tape, I've found, where the stock and the reel design were completely different according to the regional seller supply of it.
