vinyl,
12AX7/ECC82, or 12AU7/ECC82, 6692/E88CC, 6DJ8/ECC88.....etc, are basic names for a type, American/European names as I have written them above, though there are more when you count military designations.
Each type shares design and electronic characteristics...So if you need a 12AX7, all good 12AX7s will function almost the same....interchangeable, being family....but having different sound qualities and balances within that based upon vintage, specific design choices, materials, etc....
This is the beauty of tube rolling once you learn about tubes....You could get three known-to-be-nice 12AX7s....the three made by different companies, or even the same company, but different vintages (therefore construction and material variations), and have three 12AX7 sounds. Or you might find a lesser known value tube you like better!
This is also the gamble, what Steve points to. It may be a tube with a great reputation (and price), with good scores and low noise, and just not suit you as well as another. How a tube sounds is about how it is made, but also how it fits with everything else in your system/room.
Also along the lines of what Steve talked about, you can get some really good prices if the label or variation is less known/prized. You can even sometimes find British/Mullard made ECC88s...and also Siemens made tubes that are labelled RCA or GE, but also saying "made in Germany," or "made in Great Britain." These tubes are usually a good value, one, because ECC88/6DJ8 are generally less popular than E88CC/6922, and the other, that they are off-label.
Also type variants, or tubes that are electronically similar can be worth learning...Like 12BH7s (often pretty inexpensive) can usually be used in 12AU7 circuits... different, but potentially nice sound. And ECC189 and PCC189, european variations of ECC88 and PCC88s, are generally inexpensive compared to their more known family members, and can sound great in my amps.
I think what you are probably asking about is the getter rather than "gate?" A getter can be on the side, bottom/side, or top of the tube. For small signal tubes it is often on top, coming up off the top mica (the horizontal roundish shaped part that caps the vertical plates). Usually the getter riser is a wire or flat/narrow piece of metal rising vertically (or at a slight angle) off one side of the top mica, and welded to the riser, in this case, would be a horizontal O ring of metal...called a hallow getter, or O getter. Or the getter could have a D shape, a D getter, and more. You can find the getter by finding the silver flash on the tube glass. The getter "flash" comes from a heat/chemical interaction that intentionally creates a silver flash, contributing to, and keeping the vacuum in the tube.
When you have some time, you can find some good things on tube construction on the web.
Among others you can find, an intersting educational tube sales site is audiotubes.com. Brent Jessee has been at it a long time, and you can learn a lot from his site, and/or from talking with him for further clarification. He has many very rare and valuable tubes, but also some pretty good value tubes, and could be worth checking out as you learn the language of tubes. Or perhaps to buy some from a known and reliable seller who stands behind his tubes while you learn the language. I have linked his 12AX7 page since you mention it specifically.
http://www.audiotubes.com/12ax7.htmHe also sells on Ebay, as many good sellers do (big and small), and if you get into it, you can find reliable Ebay sellers you like to work with for value and quality.
This is a post I made elsewhere on the forum with some of my take on buying tubes and using ebay.
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1504652960/6#6Speaking of tube testing, noise and defective tubes, the post I linked
generally discusses finding good sellers and knowing what to look for in buying tubes....
Over quite a few years, and lots and lots of tubes bought this way, in the rare cases when tubes have been too noisy or otherwise defective, the Ebay seller has replaced them, or given a refund.
I suppose I may have been lucky, but I do check things out carefully, and ask questions if needed....and finally depend on the Ebay system. I believe I have only had to get Ebay to get a tube seller to do the right thing once....the other times something was wrong, the seller setting things straight without intervention.
So it can take some exploration to get more familiar with the languages of tubes, and to get clearer on reliable sellers, but can be a lot of fun if the quest suits you. And sometimes you can find some really great tubes and really good values.