Agree with carlsbad…Unless you are buying and selling tubes or are bored and want to dig into tubes and tinker with testers just locate a repair shop that tests tubes or testing service like the one on the link below. I was considering buying one until I researched it and talked to experts. The affordable testers in good working order only tell you if a tube is good meeting the standard. If you buy a one that has the capability to measure GM, match etc. ,which are expensive, they have to maintained and calibrated regularly.
Tube testing service example: https://www.western-glow.com/vaccum-tube-testing-matching/
Tube tester?
Hello! I have tube amplifiers, and I have ordered tubes for my amplifiers, but I don’t know how to read their quality, available, power, longevity, and how they are rated. Does anyone know which tube tester will work for CARY tube amps? Do I need to spend a lot of money? How do you read tubes that are marked :(I.e) 95/91 or 46/41