@Hoss @dj @ArdainianRight @Soy_Magnus Rounded surface. They could only really stencil it. Machine engraving was only for flats.
If you're talking about stamping, you need something on the inside and it's a pain in the butt to follow the curve so none of the metal deforms.
Even ring hallmarks driven into curved brass deform the band and require hammering out.
It's above the pay grade of the average salesperson, and the people ordering this weren't paying pro engraver prices..