+1 to above, there are no factory complete East German guns. You're going to be looking at a parts/kit build, which could range from awesome to fuuuuu depending on who built it out of what parts.
Earlier kits would be matching numbers with a real combloc barrel. After the barrel ban, the kits would need built with another barrel, which could be another combloc one like Romanian or Polish, or US from good to shitty levels of quality. Unlined steel, nitrided, chrome, etc. It all depended on who built it and how dedicated they were to making it nice. Some of the later "kits" are just mixmaster East German parts put together which would have little value to me.
Best bet would be to get details on receiver markings as to who made it. If it's just a random receiver, you'd have to inspect it to get an idea of how well it was built. Are the rivets evenly formed and flush with the receiver? Serials matching on anything? What's the barrel look like held up to the light?