Telefunken red tip

Anyone have any insight as to why Telefunken marked in red the very tip of some of their ecc82's?I'm guessing it went through perhaps special screening for medical or specialized equipment?
does the body of the tube have a rectangular 'spot' anywhere on it?

something that looks like there may have been a cloth sticker on it at some time?

... there are lots of rumors about the red tip tubes; dunno if any of them are true... medical useage is one of them (more reliable)
From Brent Jessie Web Site (

MATCHED PAIRS 12AU7/ECC82 Telefunken RED TIP ribbed plate, Tektronix SELECTED TUBE MATCHED PAIR diamond mark, VERY RARE!
New Old Stock in white boxes. These are the nearly extinct SELECTED TUBE with the cloth or foil "Selected Tube" label and the red tips. This identifies the tube as having passed intense quality screening for critical applications in Tektronix industrial equipment. Low noise and no microphonics were just two of the attributes to qualify these for exacting test and medical equipment use. These wonderful vintage tubes are vanishing at an alarming rate. A fantastic, long-lived tube with unequalled sound quality. These are hand selected and matched to within 2 percent transconductance. The rib plate are virtually identical to the smooth plate, but audiophiles note that the lower midrange is fuller. Try them and pocket the savings! The cream of the crop, better get some now!
Brent Jesse has the best historical pedigree of tubes around on his site.
He's also a pleasure to talk to.
randy-11, not a trace of it having that sticker attached at one time. That’s what made me suspicious it might be a fake. (I’m a New England yankee, we’re suspicious of all great deals!) That and the fact that it looks TOO nice. I mean it is pristine. But, the internals appear to be identical to legitimate Tele’s, wiring, halo getter, etc...The diamond on the bottom to me looks to be raised and not laser etched, a sure sign of a fake. I can’t test it in my system for the foreseeable future due to a move and lack of a dedicated sound room for the time being. I think I will ask Brent Jesse if he would be so kind as to peruse a pic of it and give me his opinion...
put a magnifier on it and see if the red tip is paint or inside the glass

the stickers were used to mark Telefunky tubes as of select quality - red tips if real and never stickered could mean a lot of things...

OTOH, has tube manf. technology improved much since ALL Telefunky tubes were made?

and who would make better tubes than the Germans?

so if you don't have the Porsche of tubes, you probably have the the BMW of tubes
Brent is extremely knowledgeable and  a nice guy.   I have a few NOS tubes that were from him that I got in a trade.   High quality and geuine,  he is one of the best sources for NOS tubes out there.
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