I got this unmarked screw back “Eisernes Kreuz 1. Klasse” today from a trusted seller, who said this was possibly early war item, I paid $300 USD. However I was later told by someone that this looks fake, seems like a "one piece construction", he also asked me to do a magnet test to test the iron core, which failed. If it is not iron core, what could it be?
I am very confused right now and would like some honest opinions from experts.

Thanks!