For Tube Folks...

Use the new tube, it's the way to go. You are trouble free.Tung Sol is good enough for me and it's lifespan is very long.

@ghdprentice   once I went to your pictures - it appears you are quite the photographer. Thoroughly enjoyed some of your city shots after the tubes.

You know how to make a camera sing !

@firberger 

Thank you.

If you want really well matched output tubes you need to burn them in for awhile and retest. They will drift around a bit when they are new. Unless you are curve tracing, you will need to test under the conditions of your amp. Fixed bias amps usually allow for adjusting the balance of the bias current in the output transformer so perfect match is then not necessary. With cathode bias you will want to be closer. If a tube is going to fail from a defect, it will most likely fail in the first 100 hours. Also, in my experience it takes tubes 50-100 hours before they sound the best. For me it doesn't make sense trying to locate matched NOS output tubes. I would suggest finding current production output tubes that you like and stock up. And if the dealer burns them in first before testing I would consider that a good thing.

As for boxes, tubes from the 1950's & 60's the boxes used cardboard with a high acid residue that over time turns them a brownish color and makes the cardboard very brittle. Just opening the box to test can damage the packaging.  

I still own a quad of matched GE 6550’s. I have them because they are a superb sounding tube and quite robust. I removed them from a Melos tube amp that I bought new and that used these as the power tubes. Replaced them after just a few hours use with a quad of KT88’s, which gave me a little more power.

If the GE 6550’s that you bought work well in your system, then you have some of the best power tubes out there. I went through a number of tube amps in the interim years, some with Winged C 6550’s, still have the GE’s to this day..if that tells you something.