Very true Tom, well I figure there are only a couple of options (3 I can think of)
1. Its barrel was replaced (which would be possible but a trick to find an east german)
2. Never marked
3. Brought to Canada or other country and came across our border
#3 is very possible, I know that years ago lots of folks went hunting over the ice - Canada to USA and back - folks not even trying to do anything wrong, they simply have done it for years