Oldest machine

Tony Duell wrote: That made we wonder... what's the oldest *operational* digital machine owned by anyone on this list? Although I suppose it's hard to define 'machine' - something with RAM, I/O in some form, and at least one CPU (what the heck do you call a CPU when it's no longer central?) I remember the discussions a while back about age of list members, but I don't recall ever seeing a similar one about age of collections! Not having all the peripherals that would have perhaps originally gone with the machine is acceptable I think (I can see some people having room for a mainframe and control desk, but probably not for a bazillion tape / drum units to go with it!). But other than that, make it complete (i.e. things like the single rack of EDSAC that we have - whilst perhaps "operational" - doesn't count :) (I'd quite like to hear responses from people with analogue machines too, but someone else will be able to define qualifying rules much better than I can) Just out of curiosity! cheers Jules