I have a, no doubt mass-produced but hand-painted, "family crest" which is much as you described, however, it is reversed: the left or top portion of the shield is white with a blue flower, and the right or bottom portion is blue with a white flower. It is surmounted by a helmet, which has something like a horseshoe on top of it. The horseshoe is white over blue on the left & blue over white on the right, with a white flower in the center. But I wonder if this is just something the "crest factories" fabricate. Yet, perhaps there is something to it. I will look up the Diehm arms in the armorials at the Library of Congress today, & report back.