For the permanent record, here is the image in the eBay
lot link above:
Let's talk about the two stamps.
1. The first stamp reads "TWO CENTS" across the bottom, thus can only be 344 or 384.
2. The second stamp is a type I, clearly lacking the type Ia characteristics of the toga button and toga rope. It can only be 409 or 482, but read onward.
3. You ask about genuine vs fake Schermack perfs. The best way is to examine a group of them and learn the characteristics by experience. Specifically, the squareness of the slot and the spacing between the two slots. The first stamp looks correct. The second stamp has non-typical angled cuts which scream to me that someone has taken a normal imperforate 409 or 482 and tried (poorly) to add their own mimic of Schermack perfs.
Bottom line ... if you want a 482A, buy one with a cert or take the time to learn the finer points, otherwise it is swimming in deep water without a life guard.