Paul wrote:

There was a time when the "free upgrade" was aggressively
pushed, such that if Windows Update was running on Windows 7 SP1,
you could have a copy of Windows 10 "pushed" at you.

This machine was purchased with Win10 Home, the predecessor machine had
Win7 Pro (but now has linux) I changed the product code on this machine
for the code from the sticker on the predecessor and it re-activated
with Win10 Pro.