Is it possible to determine to an approximate degree, the revolutions per minute of a fan, for example a pedesal fan pictured below, without using some electronic/mechanical measuring device?

One thing that comes to mind is the markings on a DJ's record player - can that concept somehow be used to make marks on a fan blade to determine it's RPM? Or can something called a "strobe tuner" help:

Can I maybe make markings on a fan with a marker and figure out the RPM using nothing else but a stopwatch? Or maybe some other DIY technique that does not require the purchase of any measuring device?

Ps. I'm not entirely sure if this is a physics or engineering question, so please feel free to move it to the appropriate site (I checked all 58 stackexchange sites and only the Physics site seemed to fit the question)