I received the key quickly and found…
I received the key quickly and found out that this was a "clean install" only situation and was not able to "upgrade" my existing system to Windows 10. This is a little frustrating as I am not willing to wipe this system clean in order to install Windows 10. I will keep the key for future use but beware, I was not expecting a "no upgrade" path ... I may have missed it in passing, which would be my fault, but I usually catch that sort of thing.