[Ron Wood]

Dwight,
That was precisely my take on the sight construction. A homebrew modification of a later sight blade with length of silver wire silver soldered into a hole drilled in the sight blade. Another possibility is that the wire was laid into a channel filed into the original sight blade and the rear blued portion soldered on top. I believe you can see a bit of silver solder emerging from the bottom rear of the blade. For restoration I would think it would be best to replace the blade with an original type. As it is, the only option is to rust blue the blade, for as Thor has noted, fire blueing would destroy the silver insert.