Tiny Bohemian Copper Coin

One of my most recent coin purchases was a teensy tiny (13 mm diameter and very thin) one-sided very old looking copper coin. Probably worth the $2 I paid for it, just asking what it is
After some extensive Googling (as well as looking at the coin), I'm fairly sure that the legend (on the edge) is [FE]R:II.D.G.R.B - i.e. Ferdinand II of Bohemia. However, all the links I found referred to silver coins of various size, and this one was clearly copper (if about the smallest copper coin I've ever seen).
Unfortunately, the first two letters - as well as most of the central device - are covered by some kind of surplus metal (an error I'm all too often seeing on 17th and 18th century coins); still, enough remains that I'm fairly positive of the ruler/country identification (it does look like a Bohemian lion in the remaining parts of the central device). Also, the other side is completely blank but for a slight outward bulging almost exactly opposite where the lion should've been; I hope it actually was blank in the first place (as opposed to being worn smooth, which is unfortunately also a possibility).
As such, I'll be very interested in the possible date range for the coin, as well as where the date area is if any (in case enough of the date is left for identifying it, which currently actually seems likely). Actual name of the denomination would also be helpful so that I'll be able to use the NGC price guide (then again, it doesn't seem to list any denomination that could possibly refer to such a tiny copper coin).

So what, how?
January First-of-May


PS: No photo, sorry. I have such a crappy camera anyway that a photo would've been unlikely to give you more than just the coin's scale (i.e. what does that 13 millimeters looks like - hint: it's really teensy tiny).