Set 3 Blue Danube Onion Ashtrays Porcelain Japan Rectangular Backstamp Vintage

Set of 3 ashtrays by Blue Danube of Japan. The rectangular banner backstamp was used between 1951 and 1976. These could be used for any other purpose like soap dishes. Measure 3.75" across. Condition overall excellent--a couple spots here and there but no chips or cracks. Smoke- and pet-free home.