M180907a
Crown above "CZECHO SLOVAKIA" with additional doughnut mark reading "MADE IN CZECHOSLOVAKIA".
Before I get too complicated, let me just say that the mark shown here and M210906 are the only two combinations of marks which show a possible producer/distributor/studio mark alongside a doughnut-shaped mark commonly believed to be a generic export mark. Bear in mind that basic similarities in marks often mean nothing, but you have to admit that the doughnut-shaped mark shown here looks pretty similar to M090616.
M180907a
Crown above "CZECHO SLOVAKIA" with additional doughnut mark reading "MADE IN CZECHOSLOVAKIA".