Early 3M Computer Tape Type Numbers

I'm trying to figure out what were the earliest Type numbers for 3M -inch reel-to-reel computer tape As best I can find, 3M began marketing a Type 777 computer tape about 1967. The Type 700 appears to be somewhat later. But 3M sold computer tape directly to at least government customers (e.g. NSA, Social Security) in the 1950s. The also notably OEMed tape to IBM who rebranded it under an IBM label until the late 1960s at which point with the help of Sony IBM began manufacturing its own computer tape. Anyone have any idea of the Type number for 3M computer tapes earlier than Type 777? There might be a place for some of these older Types at the CHM if anyone knows of any still in existence. Tom PS: There is a lot of information on 3M audio tape Type numbers as at http://www.aes.org/aeshc/docs/3mtape/aorprod-cust.pdf but computer tape seems to be an orphan