This is a piano key. It belongs to a piano that we inherited from my sister-in-law, who inherited it from the school where she worked, who inherited it from a church sometime in the 1940s. We think it's about 90 years old.
The previous owners had the tuner sign and date this key when they maintained the piano. This is convenient, because you already have the piano disassembled, and you're looking right at the key anyway, so might as well. And then when you've got the piano disassembled because you're maintaining it, and you're looking at the key, you can see when you had it maintained last.
However, the time when you really need to know "when did I get the piano maintained" isn't when you have the piano disassembled: it's when you're thinking about getting the piano maintained again. The real place you want it is in a calendar or a journal, outside the piano.
Likewise, you generally care about the change history of your source when you're looking at the source control tool, trying to understand how it changed over time--not when you're down in the bowels of the code.
I mean, it's neat to have something to read while you have the piano disassembled, but that's not really the best place to store the data.