Hello SIGCIS, I've been emailing back and forth with Allan and David, and we appear to have converged on a sense that a 400 lb roll might plausibly been around 4 feet in diameter and that photos of the SSEC show space for rolls of at least 3 feet in diameter, maybe as much as 4. So I am inclined to credit the testimony of Grosch as being at most a small exaggeration. If you look at one of the classic SSEC images at http://www.columbia.edu/cu/computinghistory/ssec.html, the tape rolls are the three large round things at the top of the machine on the back wall. Each punch was directly above 10 tape readers, and it appears that the tape emerging from the punch could be threaded through all 10 readers to create a buffer memory with 10 chances to read each piece of data. So with that and the hard drive platter taken care of, here is my next batch of candidate records. I am trying a "power of 10" approach to computer sales (or in the early days, leasing) records with the first machine to hit each milestone. This has the advantage that I don't need to try to figure out exactly with of the many estimates of CBM 64 and iPhone 6 sales are accurate, just satisfy myself that they were the first to exceed the threshold. Installed base in excess of. first achieved by. during sales years. 10 IBM 701 1952-1954 100 Probably IBM 650 1954-1962 1,000 IBM 650 1954-1962 10,000 IBM 1401 1959-1971 100,000 TRS-80 Model 1 1977-1980 1,000,000 CBM VIC 20 1981-1985 10,000,000 CBM 64 1982-1994 100,000,000 Apple iPhone 6 2014-2018 Points of possible uncertainty: 1: was the IBM 650 the first to 100 as well as to 1,000? Seems likely. 2: At the time that Commodore claimed the VIC 20 as the first million selling computer, claims were also made for the ZX81 as the first computer to sell a million. If anyone wants to make a case for Sinclair I will listen. 3: In case any Apple fans are about to speak up, re the idea that the TRS-80 was first to sell 100K, let me explain my logic preemptively. I am going from a combination of this advertisement from Computer World 18 Oct, 1979 celebrating 100,000 sold: https://books.google.com.au/books?id=UaKuzwnEiRMC <https://books.google.com.au/books?id=UaKuzwnEiRMC&printsec=frontcover&sourc e=gbs_ge_summary_r&cad=0#v=onepage&q&f=false> &printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false and these plausible seeming estimates of Apple II sales by model (https://retrocomputing.stackexchange.com/questions/459/over-its-lifetime-ho w-many-apple-ii-computers-were-sold), which suggest only 65K sales of the original Apple II. As Radio Shack must have written the copy somewhat prior to the magazine date, say in mid-September it is had to imagine that the Apple II Plus, introduced in June 1979, sold 35K in its first three months to make up the difference (actually more than 35K sales would be needed, to cover however many of the original model were sold between Sept 1979 and its withdrawal in 1981). Apple II sales did not peak until well into the 1980s, so although the Apple IIe eventually sold millions I believe the VIC 20 got to the one million milestone first. Best wishes, Tom