Identify: IBM memory

http://gizmodo.com/5878645/this-giant-chunk-of-metal-is-4-kilobytes-of-memor y But what type of memory is it? Delay line, CRT tube, Drum? Bonuspoints if the machine can be identified :) Note that I have put these thoughts in the order I had them or researched updates - this makes some of the earlier reasoning incorrect :-) First, I wouldn't necessarily rely on the description ... the machines with memory width in "bytes" did not come into use until significantly later than valves (vacuum tubes) ceased being used for anything other than displays. The top two cylinders certainly look as if they contain crts, but as far as I am aware Williams Tubes were a British idea that wasn't used by IBM** (and I thought that they were about 5" diameter at the face plate whereas these can be at most 3"). They also don't look like delay lines or anything motorised (nobody would so easily (!) carry anything of that era that had rotating memory). OK, I'm wrong here - the IBM701 and 702 apparently had Williams Tubes Further web searches lead me to the IBM 706 which was the main memory of the IBM 701 system. The object looks like one of the 18 units that together provided 2K 36 bit words of storage (and thus provides 4K bits, not bytes, of memory). (and, yes, these are 3" diameter at the face plate) Think that has nailed it. Andy