Oldest Software Seen in Production?

Ian Bevan asks: "In my last job we were replacing a legacy system, written in COBOL and running on a Fujitsu mainframe since 1985 (it was a payroll application). A bespoke database application I wrote in 1989 was still being used, unmodified, last year. What's the oldest software you know of still in production? Anybody know of anything from the 70s, or even 60s ? What's it used for?" Has anyone seen software in production that is older than they are?