This is almost certainly an East German Dummy round. The black “paint” is most likely a continuation of the plastic of the upper portion of the dummy, that is extruded down into a hole through the steel base, forming a snap cap and helping to anchor the two pieces together. I have several variations of this dummy. Earlier East German Black plastic dummies, made in many calibers by the way, had a small firing pin clearance “dimple” in the base - the plastic did not go all the way thru. Tomorrow, I will try to scan a few sectioned 9mm Makarovs, and perhaps a .32 auto dummy and get my friend Joe to post them on this forum, so that you can see the typical construction. I don’t have a sectioned 7.62 x 54R, but construction is similar.