It is definately a Playmbil crown; the very first "male" type to be more precise.
(sets 3130, 3131, 3138, 3261-v1 and 3331-v1 from 1974-1975)
In 1976 the shape was changed; it then included in the middle the bulbous part of the 1st knight-helmet. (see f.e. 3331-v2)