I bought these new around 10 years ago when I was running a Berning Siegfried 300b OTL amp. The amp was used mainly with WE and KR valves, and these remained in their box for the most part. I really can’t remember how much I used them, but let’s say 100 hours to be on the safe side (in reality I know it’s much less than this).
From recollection they sounded very nice on the Berning – kind of midway between the lush WEs and the more pinpoint KRs.
Not sure how easy these are to find nowadays…
Feel free to ask any questions.