Assume an aperture of f/166 and an ISO 100 then
f/128 at 64 is the same (2/3 stop)
f/90 at 120 is the same
f/64 at 250 is the same
f/32 at 500 is the same
So if I set the meter at ISO 500 take a reading and set the stop at 32
it should tell me exposure time - reciprocity at f/166?