A few more thoughts after rereading this thread:
1- Columbia tapes. including reels were numerically the same as LP's. The alpha prefix is the format designation. CR is for reel. C, KC, PC, JC were for LP's, and the letter preceding the C was the list price designation. Many SQ LP's had a sticker and a new prefix given later to increase the price by $1. The only exceptions to these rules were that the few Quad titles that predated the five digit numbers, like Super Session which used the previous four digits, were renumbered with five digits. The other exceptions are later CD issues. If remastered and/or bonus tracks added, titles were given a new number.
2- Most early Columbia reels were of easy listening, jazz, and classical because that was nearly their entire output until the late '60's. Any title that sold reasonably well on Columbia/Epic was released on reel, along with a few they expected to sell well, but didn't. I have a reel of Illinois Speed Press, which didn't exactly fly off the shelves.
3- Yes, the CTI (Creed Taylor Inc.) reels, including the Quads were custom pressed by Columbia. At that point, all CTI/Kudu product was pressed by CBS. In '74, CTI/Kudu switched to Motown. Although Quad was dead at that point, the SQ masters were used for all Motown CTI/Kudu titles that had been previously released as Quad. Matrix #'s in the grooves say SQ. In '78 when departing from Motown, Taylor settled by turning over Grover Washington's contract and Kudu masters to Motown. Later, Bob James acquired the masters for his CTI albums. In 1978, CTI went into bankruptcy and has been distributed and owned by Epic (today Sony) ever since. In '89, Creed Taylor tried unsuccessfully to reacquire his masters from CBS.