​Interesting ...   My source was (is) my friend and former colleague from Stellar, Russ Robelen, ​who was the HW lead for the 360/50 and the IBM ACS systems.   Russ said the original IBM project Winchester  first begat the platter (as Noel pointed out was so named because of the 30-30 capacity of the original disk) - which showed up in the 3330 disks as well as the sealed head stuff that Paul and Greg are talking about.  What I never asked him, was where Memorex fit it.  It was a somehow a joint project with them, and they got at least some of the technology -- in fact DEC's OEM for the RP05/RP06 was Memorex [the big box of logic on the side of the DEC version was the Massbus to IBM I/O logic converter].    It is also true that real lasting piece of project Winchester was the embedded (sealed head) stuff that came from the 3340.

I should ask Russ what he remembers, on this.  I'm guessing that maybe there was two parts of the project.   The sealed head stuff that Paul and Greg are discussing and probably was IBM only, as I do not remember that Memorex ever produced a similar product to the 3340 .   But maybe platter stuff may have been joint.

But I have asked Russ a couple of times, and he very much states that name 'Project Winchester' came from the platter technology which was first introduced in the IBM 3330.

I'll have to dig up the book Noel suggests and see what they see (and ask Russ what he thinks of it).