Oldest computer you've used for "real work"?

[Chris Randle (UK)]

Still use my 16C (computer?) at work most days. Bought new from Educalc in 1994; manufactured in 1988 (2817A...), so it's 26 years old, although I've owned it for only 20 years.

Probably not that impressive an age compared to some, but what I find amazing is that there's still no better tool for working in hex/binary/decimal and flipping between word sizes and complement modes.