Something's wrong here. The stem material Dunhill used was top-drawer stuff. No inclusions or voids, no graininess, and slow to oxidize. I've never known a exception.
Gonna guess what's on your pipe is a replacement made from a low quality molded blank. (Probably Greek by the sound of it)
A close-up pic of the of the button, both an oblique view and end-on so the slot can be seen, should settle the question.