Maybe these images will help the discussion.
Yes, the bead seems big. The blade mikes at .125 (1/8"), and the bead's widest diameter at .11; I am not sure what the standard gold bead diameter is (if there is a standard), but I would guess a 1/8" blade would ordinarily have a 1/10" bead pegged into it.
Here's a side-on image in direct light that should address the question of whether the blade is all the way down on the base. The work marks also show pretty clearly that the pin has been removed and replaced at least once, which would indicate that this is not the original sight -- or if it is the original sight, that it has been removed, modified, and replaced. But it doesn't look like a stock S&W Patridge blade to me -- it's too long front to back. It also looks to me as though the inserted part of the blade rode a little high after placement, and someone tried to file it down to the height of the base, removing a little of the base stock in the process.
And since we are talking micro-measurements, I'll throw in another rear sight image and note that the top of the notch is 1/8" wide
I'd still like to ID the sight manufacturer if possible. I acknowledge that any competent gunsmith could fabricate or adapt a sight, but I have to believe that tinkering with something readily available would be easier than starting completely from scratch.