Is it actually out of cal (spec), then?

I seem to recall that there are (were) two SmartSats:- one was hand-held, whilst the other was similar to (or the same as, most likely) the old Rigel 322. If your's is the "Rigel" type, won't
Rigel* be able to do the needful?
Regarding "which SpO2 tester" ... have you seen
this .pdf?
And don't they all have a "finger"? How else can you test a pulse oximeter c/w finger "probe"?
Unless you were thinking of the
Lightman!
* Speaking of which,
here is a nice article by our old friend, JB.
