Most any D.C. milliammeter can be use to adjust the bias on an amp

by measuring the plate current, and you can 'check' this idle current

on different tubes in the same amp for similar idle current readings.

But tube 'matching' requires monitoring the current while the tubes

are shifted through full operating conditions, not just the idle

condition.

 But it's better than NOT checking, and can be an otherwise

next-best-thing if you have a batch of unmatched tubes. Connect the

meter to shunt the output transformer. If you don't know how to do

that safely and correctly, you probably shouldn't be messin' around inside a

potentially lethal high-voltage circuit...you can buy or make adapters to connect your

meter to the tube socket instead.