spain and france also have issues of encased postage stamps, they rarely come onto the market which is why i paid over the odds for one from lyon in france.
Article about fake encased postage was in Numismatic News issue dated 1/13/15. A search of the Internet tells complete history of these things and reason they were made. If I remember, one of the major stamp auctions had a complete download of a major collection (1/2 inch thick). I have it somewhere...perhaps Siegel or Ramsey auction.
Mine is rare with ribbing on the face side, less than 30 in existence. Got it from my grandfathers uncle 50 years ago
That's like asking how many different flavors of ice cream there are I'm sure other members will chime in. A hard, round plastic case for a quarter (if it fits). Even a cardboard 2X2 works. Then put it into a sealed envelope (you can rip it open when you want to see the piece). Humidity and light are what you want to avoid. You have saved it in good condition all these years so don't get too fancy.