This mark has been bothering me for a long time. It was not shown or mentioned in any mark reference book, and I could not find any other leads whatsoever. I have heard a thesis that states this mark is indeed a retailer mark. This would not usually be unusual, but East German production was mainly geared towards items marked by the producer (combine), with custom-marked export items being rare exceptions.

M090637a
Round mark showing a fruit-bearing tree, set above "MADE IN EAST GERMANY".