If you are thinking of starting a collection (
any type of collection), ask yourself: What is the focus of my collecting? Why do I want to collect? What do I want to accomplish?
Some collections want to "catch them all", and get excited in finding rare things. I collect keyboards because I am interested in the tech, and have a desire to learn more and to in the long run contribute something to the art of keyboards.
In collecting, going out there and just getting what you want is hard. You have to watch eBay (or similar sites) regularly and wait for the opportunity to arise.
Most of my vintage keyboards were acquired at very low monetary cost, but I have spent a whole lot of time on the 'Net looking for them before I found them.
Back when I started, whenever I found a keyboard for sale, I used the old Geekhack Wiki a lot to find out what it was.
When that went down (before the existing Geekhack Wiki), I contributed to the Deskthority Wiki, and the two Wikis are now better and more useful than the old GH Wiki was.
I just found a 'Win 95 IBM Keyboard' on eBay for $30...does anyone know anything about that keyboard? I would post a link but I don't want anyone to buy it before I can 
You need images, to compare to other keyboards. Or go by the model numbers or FCC IDs on keyboard's label.
Keyword spamming is rampant on eBay, and eBay does not want to do anything about that. "IBM" usually means only "IBM-compatible". "Clicky" is often misused because unlike us, eBay considers "clicky" to be a "subjective term" (their words in a reply from when someone here complained to them) ....

Most vintage keyboards with Windows keys (for Win95 and later) are not mechanical, but there are some exceptions. The Dell AT101W for instance.