@Mr-Moloch Ah! Gotcha - I have no idea of it!
Specifically, what I meant is that the NPC for my shop told me he didnt "want to get into trouble by peddling this". So it was probably marked as stolen.
I'll keep an eye out for other stuff like the Grapple gun.
As for the Amaurian set - cannot judge whether it should or not be marked as stlen. The idea of NPC shops is to allow goods to circulate between players without having them be NPC things like setting up a stall and waiting there, tho, so maybe these items should be allowed?