Can not get mode() to return '!'

[Chainsaw]

Hello,

system: gVim on Windows 10 Pro 64-bit.

I am reworking my statusline and titlestring, and have a question
about the mode() function.

Using :set statusline=%{mode()}, and :help mode() as a reference, I have
tested every return value for mode() that I might need.  However, I
tried many different Shell and external commands, and
can not get mode() to return '!'.

Any help would be appreciated.

Thank you.