Mike,

Because engraving tools provide a "facet cut" similar to precious stone cutting. Look closely at the lettering and it is sunken to a U shaped trough at the bottom. Though the original die was cut by a skilled die sinker/engraver and recut over its (usable) life.

There again if you look at a Rigby double or similar it is quite a different matter as the name and address were hand cut.

A mate of mine spent 50 years in the trade working on both dies and gun/ jewellery projects and taught me much of what he knew. BTW I've seen everything from his work to Durs Egg and other great makers.

Underlever (a forum member) and professional engraver can provide a more lucid explanation than this as to how the gravers are shaped to produce various effects.

I think the machinery to do such has fallen out of favour.