So you've landed the white whale. What next?

Hunting tubes this weekend and talked to a woman whose dad built and repaired hifi equipment. She says she has gear that's been locked away for 50 years.

I show up and see a table covered with old gear adorned with 15 or so tubes, and it was almost comical. The husband remarked on the Genelex Gold Lion KT-88s "they look burnt out to me. look at those spots in the sides." Those would have been the flashing on the two side getters. Then I carefully pulled the Mullard 5AR4/GZ34 rectifier branded Amperex Bugle Boy with. Blackburn codes. Next was a Tung Sol 6v6 GTA, then what appeared to be an RCA black plate 6L6.

So here's the thing. I scored huge. Should probably never hunt tubes again lest I incur the wrath of the gods. Question is, since I don't own a tube tester, do I dare pop these tubes into my gear to see how they work? Related question-- I get confused as to what a tube tester really measures. A lot of people I respect say a tube tester tells you almost nothing, but what's a good way to ensure tubes of unknown provenance are safe to use? I'm sure someone will suggest I send the tubes to him for testing and safe keeping. Perhaps there's another way?
Lucky you! Unfortunately though, you don't want to mess around with rectifier or output tubes unless you know their condition. These can damage the circuitry if they are bad. Small signal tubes like 12AX7 or 6SN7, etc. are another story and less likely to cause damage though they can in extreme cases. If you are tempted though, at the very least try to use them in the same pairings from the gear they came out of and watch and listen to your amp closely for trouble. If you think no one in your area can provide testing or matching for you, look in the direction of musical instrument amp people. Even the local music/guitar store may be able to test and match tubes for you.
Harv, the funny thing is I'm least afraid of the rectifier tube, since those things tend to last a really long time. Also, the output tubes are used as drivers for 845 tubes in my integrated, rather than as "output tubes" per se. There's a guy not too long a drive from me who runs a site called The Tube Museum, who offers rigorous testing on an Amplitrex rig, for a fee. Was thinking about taking a drive to see him.

This experience has me hooked on tube hunting, so I'm prepared to purchase a tube tester, but I've always been confused about what they really tell you.
Call Moby Dick!!
I would test them.
I probably should have tested them but I just couldn't wait. After talking to my dealer, I inserted first the Mullard Rectifier, then about 30 minutes later, the Gold Lions, watched closely to make sure the plates didn't glow orange and kept an ear out for any problems with the audio. Adjusted bias after about 10 minutes of play and sat back and enjoyed some lovely music. The amp held its new bias perfectly for the duration I listened. I'll need some more experience with the new sound before making any serious critical conclusions. I'm kind of hoping I don't fall in love with the Gold Lions, b/c that would become a very expensive habit.

The Line Magnetic amp I'm using is pretty hearty. I have no problem unplugging a speaker cable during operation to change output taps and it happily drives 8 ohm speakers off the 16 ohm taps.

Having said all that, anybody have a recommendation for a reasonably priced, compact tube tester that is reliable and somewhat easy to use?
Is the Tube Museum guy in Tuxedo Park? One of my favorite places~
Yes, it's in Tuxedo Park. Not too bad a drive from the city and there's good golf nearby too! Good to get the recommendation on the Tube museum. Give me some comfort in using them. From your post it sounds like you've actually been there or just one of your favorite places to buy from or send your tubes?
I looked up his website. He apparently lives in the old Loomis house. Loomis was a wealthy dilettante much interested in science and contributed to various military research endeavors during WWII- there is a pretty good book about the subject that was published a few years ago.
My familiarity with the neighborhood was my interest in living there before we bought our current house- it is made up of old mansions, some in ruins, that were built between the 1880's and 1920's. The place was abandoned by the many after the '29 Wall St. crash. Some of the houses are glorious and far cheaper than what they would be worth in a location closer to Manhattan. (Sloatsburg, the town outside of the wall, isn't a garden spot either, so it's a desolate location). I love the gothic creepiness of the whole place.
BTW, I have a B&K 747 that was given to me. I'm happy to loan it to you if you can get it calibrated. It appears to be pristine, with the books.
PS- I didn't intend to endorse the Tube Museum- I don't know one way or the other -I have not done business with him. I just remembered that he seemed to appear about 5 or so years ago, and I thought i remembered that he was based in Tuxedo. Thus, my original question. My comment about it being my 'favorite place' related to the location, not the business.
If I lived there, I'd probably be selling parts of Dr. Frankenstein's lab. It's got that kind of vibe. :)
Glad to know about it and very generous offer on the tube tester. I'm just going to have to buy one at some point.

I like Tuxedo Park a lot. Agreed that it's a very interesting and isolated community. Also interesting price point on the homes there. The barrier to entry is high, but there are absolute castles available there at prices that are a fraction of what you'd expect that close to NYC, although in absolute terms, they're quite dear. A good friend lives there and we play golf at the Tuxedo Club. A very nice spot to have a post-round drink.