Gm Tested at 5200/4500 & 5600/5300
on a calibrated Triplett 3444 tube tester
where the Good range is 2000/2000 & 3100/3100
*Paul Hart calibrated/modified Westmore 501 (Triplett 3444)
Test results may differ between various testers for many reasons such as technical design, aging components, etc. So while test results are a good indication of quality there can be some difference between the many differently designed & maintained testers.