Best tools to calibrate TT motor actual speed?

A fellow member, Lewm , was kind enough to sell me his old Walker motor controller for my Nottingham Analogue TT.
It is in good working order but now I find I need to acquire a method ,or tools may be best phrase , to calibrate my TT motor speed exactly.
Never having any adjustments available for TT motor speed it is not something I had given any thought to.

Lewm did mention a KAB strobe which uses a disc and a battery powered strobe.
Also a quick perusal reveals various manufacturers of marked platter discs where you would use a mains powered light ( to establish 60hz I assume) to check actual speed.
What does anybody here use or has used in the past that is easy, reliable, accurate and fairly priced?
Thank you