Don’t do it, almost all rare types that appear on eBay are fakes, from Shenzen and similar locations.
Certain parts are no longer available and that’s a certainty. If an unavailable part suddenly is available on eBay, from China, just walk away. Trust me, there are lots of parts that I wish were still available, but they aren’t and we move on.
Sure, there might occasionally be an old guy in Poland with a box of special unavailable parts in his garage, but the listing will clarify that. Everything else, like classic Hitachi 2SJ56 and 2SK176, VFETs, rare STK modules etc listed on eBay are fakes.
Because they are no longer available, unscrupulous sellers know that buyers are willing to do almost anything to get hold of these mystical parts. So they take existing low-spec parts and have them printed with whatever the unavailable part name might be. You install the part, it fails, and how are you going to prove the new part is fake, versus there being some other reason it failed..?
In many cases, you don’t need these parts anyway. For example, I have access to parts vendors that sell NOS parts and keep many NOS parts in stock. There are modern replacements in many cases too, so don’t pay for fake parts.