Hi Warren,
Here is the patent filed by IBM on Christmas Eve 1954 and issued in May 1964.
http://www.google.com/patents?id=gQR...page&q&f=false
The IBM 305 RAMAC was the model number for the entire computer system and
the disk storage unit was the IBM 350.
I have some 14" platters somewhere here from what I recollect were from a IBM 2316
removable disk pack dating from the mid 60's which were used with a System/360
machine.
If you happened to be in the machine room at the time one of these disk storage
units experienced a head crash, it was a sound you do not forget.