It must be magic dirt.It looks like they had a protective coating of dirt.
I don't think a modern keyboard would stand a chance. But back then things were generally built to last.You can sort of understand how the electronics could last that long but it seems really remarkable that the keyboard still works, especially considering that environment.
My oldest machine is a 50 MHz 486DX from 1991. Like yours, it has been some time since it's been booted up.If they were the original purchaser, I'd say they certainly got bang for their buck.
I think the oldest still functioning computer I have is a 133Mhz Cyrix CPU based PC from 1997. Well, lets just say it was functioning when I last shut it down in 2003, I think? It's stored in my basment somewhere, lol
My circa 1978 TRS-80 Model I still functions. But the monitor quit. Also, a 1984 Model 100.My oldest machine is a 50 MHz 486DX from 1991. Like yours, it has been some time since it's been booted up.