A friend discovered that one of the more modern pieces of equipment instrumenting those old signals was an ancient WYSE terminal from the late 90s that had been bricked over during a station project.

They moved a booth or something and the compartment it was stuffed in was missed during the cleanout. The thing was working for at least 20 years and may still be there!

I worked with a client that had a cash disbursement system working on an ancient dBase 16-bit application. They had a very difficult to change process that required multiple transactions because the system couldn't represent the dollar amounts appropriately.