The book that got me started 47
Popular Mechanics hoax
Jim Stewart You bet. Though trombone slides, which accomplish very much the same sort of thing, have been around since the 15th century or so. By the way...
Could well be, I don't know any history of the ICL UDR, but suspect that not very many were made-sold. It was a fairly exoctic device for the time and I only ever came across the one.
Cheque readers must have used similar technology, but were more specific in their needs.
The ICL UDR was both OMR and OCR (you needed a special stylised character set), but could only do one or the other on one pbutt. If you wanted to read both marks and characters (we did) the document went round the read drum twice, once for OMR and once for OCR. There could be up to 12(IIRC) stackers in units of 3 (ie 3, 6 9 or 12 stackers) which could be selected by program, BUT the program was time critical and you only had a certain time between the read finishing and having to send the stacker select command.
As I recall the UDR itself was about the size of a fast line printer, with second similar size box of electronics.
I will, eventually, add some more details of this device to my ICL1900 web site.