Beautiful Oscar Schlegelmilch Ashtray 5756 s

Picked this up at a thrift store - loved the cerulean blue color and the abstract image in the middle. Just trying to find help identifying an era, or anything else about it. Markings say 'Oscar Schlegelmilch 5756 s'. I believe it's ceramic. It has traces of what used to be a gold trim around the outside edges. 6 inches across on each of it's 3 sides. I've tried internet searches and other forums and I'm coming up short on trying to figure out when it was made - or if it has close relatives.