Groove Tubes GT-6CA7-GE vs NO GE and NOS Sylvania

Anybody heard the difference between authentic NOS General Electric 6CA7's and the Groove Tubes GT-6CA7-GE? And what about the NOS Sylvania 6CA7' would they compare?

Any input is most welcome
I've been using the NOS Groove Tubes for some time. Amazingly strong, clean and accurate. They don't sweeten or mellow the sound like some and appear to have pretty flat response. To me, these are worth as much as NOS Mullards and I like the sound better.
Elevick: Are all 6CA7 Groove Tubes NOS tubes? In other woors, would you recommend any Grove Tube 6CA7 (in good condition, of course)?
I would be careful. There have been reissues as well as many different years. My quad has been carefully matched and has the tech's codes on them. If you are really interested, email me and I'll send you a photo of mine for reference. I am 100% positive of the quality on mine.

I have not been able to locate a matched quad of Groove Tubes GT-6CA7-GE. Only the GT EL34-M is currently available, and even some of these are now being sold by new GT owner Fender with stickers on the glass rather than the original imprinted orange GT logo and numeric information. I have a question for you since you've used Groove Tubes: The tubes come in rating ranges from low - mid - high. Seems everyone selling GT's has a different answer on which rating range of GT's to buy for audio HiFi applications. No consensus at all. What rating were your GT's? One HiFi buyers conundrum with tube reissue purchase is that most resellers are coming from the guitar amplifier world, not from the audiophile world. Nothing quite like the classical/jazz audiophile being asked by the reseller if they want their tubes for "the Van Halen sound"?
The numbers relate to how soon breakup occurs (a guitar amp issue). You want the highest number for 2 channel apps. (i.e., late breakup). Visit Doug's Tubes.