It is likely from a Dell RT7D50, or perhaps from one of the other two Dell keyboard models that look about the same as that one but are different internally. All three are very common.
You were lucky, that I had one around to compare with, otherwise you would never have known. There are hundreds of keyboards models that have keys that are quite similar in shape, but this one matched perfectly.
However, I don't know if the manufacturer makes keys that are precisely like that but for other brands.
