This can't be from the factory, would you agree? I could find no reference to the part online. I forgot to get a photo of the top of the sight, but the new piece is held in place by two very small slotted set screws.

The conversion part can probably be removed and another red insert installed.

How much does this detract from the value?

Note that the seller is calling this gun a "Rare Target Model", to which I am calling BS at this point. Your thoughts?