Hickok 6000a limitations

I recently came into possession of a Hickok 6000a. It seems to be limited on the types of tubes I can test.

Which tubes might that be?

Maybe it is just the chart but an example would be the 6S tubes . The only one on the chart is 6SN7. This is also true for the 12S tubes. The only one on the chart is 12SN7.

I just noticed that all the tubes I cannot test are metal tubes. Is there a separate chart or supplement for these types?

Yes, there most probably is a very lengthy supplement, and I suspect that you can obtain it from:

http://radioera.com

I have a Hickok 800A, and about 15 years ago I obtained the supplement for it (many pages filled with tiny print, so it would not be practical for me to reproduce it for you) from a gentleman by the name of J.W.F. Puett, of Puett Electronics in Dallas, TX. He was and/or is a prominent figure in the antique radio collecting field.

He is no longer in business, but I understand that a few years ago Radio Era Archives (url shown above) purchased Mr. Puett's inventory of literature and other items.

The supplement I have, btw, is identified as being for Hickok Models 533A, 600A, and 605A, but I have never had a problem using the settings it lists on my 800A. So keep in mind that a supplement useable with the 6000a may be identified as being for other models. The people at the link I provided may be able to advise further on that.
Regards,
-- Al

Thank you for the help.