So I'm not sure what we've got, here. The machine seems to have only one memory board in it, so, just for grins, I decided to look at the online docs on the 1900, and see if it needed memory boards in pairs. The doc described the model 1905 and the model 1955 - both of which have a "diagnostic/maintainence control panel", with lights and switches, which this machine doesn't have. Although that may not mean that much - people started getting rid of them because they cost too much, so maybe this is a later model, without them. They also have a cutout in the top panel for a large keyboard (see pictures online of these model) which again this machine doesn't have (the cutout, that is)... It does seem to have one less CPU card than one of the models (forget which one) in the online manuals (CPU cards only go from A-H on this unit, not A-J), and no, there isn't a missing CPU card, i) the slots are numbered, and ii) there's no empty slot. I looked all over it for a model/serial number placard, which would give the model, but NSFL, couldn't find one. :-( It does have a large red placard panel on the front which says 1900, so I'm pretty sure it's _some_ flavour of Burroughs 1900, but... Anyone have any idea what this thing might be, exactly? Noel