Set of 5 educational busts from the 1920s - 1930s depicting different ethnic groups

Set of 5 plaster didactic bust statues from the 1920s - 1930s, depicting 5 different ethnic groups: Negroid, Australoid, Mongoloid, Europoid, American Aboriginal, accompanied by their respective descriptions. The busts are teaching material from a teaching school. The measurements are similar for all the statues, the largest is that of the Europoid (Caucasian) with measurements 28 x 9 x 11 cm.