At the bottom right corner of Columbia back covers is usually a numeric code:
According to the eponymous WB (quoting Bruce Spitzer) these identify the following LP cover manufacturers:
‘2’ Imperial Paper Box Corp., Inc. of Brooklyn, NY
‘3’ Modern Album, Long Island, NY
‘4’ Imperial Packing Co., Inc., Indianapolis, IN
‘5’ Modern Album, Terre Haute, IN
Source: WB on Hoffman thread
These tie in with the location of Columbia’s East and Central US record plants, which makes good sense, but not from the point of view of West Coast distribution. There is a 1 code missing from WB’s list (my copy pictured below).
1 code from Columbia CL 1397 Dave Brubeck Time Out (CBS)
Logistically it is almost certainly located on the West Coast.. Anyone knows anything more, drop me a line.