Test mode message - Microsoft Community

my local museum has computer displays large message centre screen - test mode.

all i've found refers messages in corner.

how rid of it?

searching forum found this

https://answers.microsoft.com/en-us/windows/forum/windows_10-start/test-mode-windows-10-home-build-10586/44840c1b-fa9b-45a8-8413-bdfa1cb204a2

Windows / Windows 10 / Desktop, Start, & personalization / PC