pair NOS Vintage RCA 7189 block letter hi-fidelity amp power tubes

Description

This sale is for two (2) unused 7189 type power tubes from RCA. All the samples I've examined bear the codes DU or CZ, block logo lettering, and disc (or saucer) getters; I believe this dates them between 1969-early 1970s, but please feel free to offer more precise information. These tubes also have numbers in the glass, amid the pin-ring on the bases.
If a tube fails through no fault of your own within 30 days of purchase, we will exchange it for a replacement from the same stock.
Tubes are tested on a B&K 707 mutual conductance tube tester recently serviced and calibrated by Mike Mabry in Woodland, WA. Mike has been working on this series of testers for many years.
A sampling of tubes tested between 90-115, where 66 and above rates as "good" for Gm; all also had life rating of good or better (at 0-15% deviance , where 25% or less rates "good": read below for more explanation)
The test ratings on this type of B&K tester may require a bit of explanation. Their "life test" is considered "good" if the meter rating is within 25% of the Gm rating. e.g., a tube with a mutual conductance (scaled) rating of 80 would still be passable if the life test registered a 60 on the meter. Most of their test settings correspond with a 0-120 scaled reading where the "good" area is about 66 and higher on the meter.
THANK YOU for looking!