Austria stamp vs reprint

Hi ,

I need some help re the Austria 10k 1910 stamp .

I want to buy one to complete the set / page & as the cv is £200+ it is will be more than I usually spend on a single stamp !

However I’ve had a search on eBay & it seems there are reprints which look remarkably like the original apart from “Nachdrucke” ( probably removable ) on the back & I’m wondering how else can I tell that a stamp I buy is an original & not a reprint .

Many thanks

Trev