How to know you are using classic vi

:version
Version 3.7, 6/7/85.

Yes. 1985. 22 years.

On a contemporary computer, it will probably look like this:

:version
Version 4.0 (gritter) 12/25/06

(The given date will vary.) This is Gunnar Ritter’s lightly modernised fork – but still the classic vi.

Any other response means you are using a clone.