Sydney: I have done a number of these, but with gold rather than silver. Silver tarnishes and requires a good rub to bring up bright again, but that's not a serious issue. Most of these old sights either had silver or platinum, rather than gold.
If you can remove the leaf, make a fine cut vertically in the centre with an engraver or a fine saw blade. Undercut the edges carefully with a sharp needle punch...just a series of punches is all that is required. Or use a graver to undercut the edges of the cut. Lay your silver over the cut, and using a punch with a slightly domed polished head, and a light hammer, tap the nice soft metal down into the cut. File it off, polish, and blue/brown.
These vertical lines are wonderful for sight acquisition in failing light. To be most effective those leaves should slope forward. Often, the leaf itself is stippled to create a very matte surface. That silver line shows light a florescent light tube.
