How do 6SN7WGT vs 6SN7GT differ?

I have Cary WE300B SE monoblocks and a Cary SLP98P preamp. I have been purchasing back-up tubes to stash away for the future. I am confused by the broad number of GSN7 tube types available, in particular the difference between N.O.S. 6SN7WGT and 6SN7GT(A/B)tubes. Are they simply interchangeable?

I use high dB horn speakers (103dB sensitive), so I am concerned about tube noise. I have teflon tube dampers on all tubes, and these, I believe, help with microphonics.

Thank you.
The "W" is a mil-spec designation. The "GT" is the oldest, followed by the "GTA" and "GTB". The earlier are usually the better. However GT and GTA and WGT are all great. The GTB is very good if made during the first half of the production life of the GTB, and they went somewhat downhill toward the end. Still a good tube though. Any GTB, even the worst ones, are alot better than any of the newer stuff, IMO. I'd try to go for the older stuff whenever possible.

Thank you very much. I appreciate you thoughts.

Yes the W denotes military..

From a purely technical standpoint the tubes ending in GTA, GTB can handle higher voltages (max of 450 volts or 5 watts per section) than a GT can (max 300 volts or 3.5 watts per section). Therefore the GTA/GTB will run cooler.

The GTA/GTB were made for televisions commerically, and for military probably a television type display and other higher voltage applications.

If you want a quiet tube then try a 5692 tube. A 5692 tube is rated for up to 275 volts or 1.75 watts per section.
Thank you. Sugarbrie. Greg
Oh.... the most popular 5692 tubes are the RCA Red Base and the CBS Hytron. If you find any other branded 5692 tube with the same color Red Base, then it is the RCA tube. RCA made some for a few other companies.

The 5692 will generally have the lowest possibility for microphonics.
There are more points to these. The WGT is the highest voltage handling plus it has an 11 second warm up time. This prolongs tube life all around. I happen to have 8 NOS CBS 6sn7GTB tubes if you need.
Actually, it is the WGTA/GTA/GTB that has the highest voltage handling. The WGT is a military GT.
Thank you for the offer Emery. I purchased 4 more Jan-Philips 6SN7 WTGA from Angela Instruments yesterday before seeing your offer tonight.

I appreciate all of your help, and I have my eye out for the fabled 5692 tubes to try in my pre-amp. I may have to wait a month to afford those.