Playtest cards were intentionally made during early game design to test ideas, rules, and card balance
An alternative to this would be to store your cards in your container and then use tabs to create sections for the different varieties of rare card
The three players I was considering for this slot were William Jensen, Justin Gary, and Tomoharu Saito
Today, most counterfeit cards are designed to pass various tests like the bend test and the light test, and some look almost exactly like the real thing, even upon close inspection (unless you're going really deep and using a jeweler's loupe, which is a good way to weed out fakes but too much work for the average player)
Ob Nixilis, the Hate-Twisted fits this list better but should be treated more like a 5-mana removal spell with upside, or a more costly Underworld Dreams that is a different type of permanent