MC should be for "multicoated," which would make these East German Zeiss lenses of relatively recent vintage. If you can post an image of the mount, I'm sure someone here can help you identify it. If the mount is something like M42, then you can easily adapt it for Nikon. If it's not, it might be easier to find a Praktika body to use them on (not sure offhand what mount they use--Exacta?).