Thank you, Clive, from now on, every time someone asks about safelight tests, I will make sure to be precise in pointing out the matter of the necessary pre-exposure while mentioning a coin test.
May I just add, that it does make a difference to the outcome of the test when the safelight exposure is made after as opposed to before the enlarger exposure that produces the light tone. The Kodak test takes that into account, but I suppose one could modify a coin test to use two rows of coins and to make two enlarger exposures. It is just that I have never seen a coin test comprehensively include all of those important details, while the Kodak test includes them, and it is concise.
Rafal, you make a very good point, as I had not thought about applying the coin test to before and after. Exposure inertia is an important factor that I overlooked. Thanks.