Hi volkund
Sorry! It’s a well known modern reproduction. So many ways to tell…the easiest way is the modern type of the attachment. The shape of the cast badge, use of soft enamel and some kind of metal makes it very obvious that it’s a modern reproduction. You can buy as many as you like here Hitler Youth Membership Lapel Pin only $7,99 a piece
However, original HJ “Diamonds” are known from this Sudetenland manufacturer M1/143 Gebrüder Jäger from Goblenz…but that one is not one of them.
Cheers