22
Smith & Wesson Model 459, 5904 & 5906 pistol
(thelemmy.club)
Love the raw steel on the 5906 and removal of the little blinders on the rear site that seems to be normally standard and I am not exactly sure what that is even for.
it seems to be the housing for an adjustable sight - there are 5906 models both with it and without it


see also the Browning Hi-Power for another pistol with both such variants (and where the adjustable sight one also shows why you might want to have some protective wings for it, although this one's much larger, people tended to be pretty overly optimistic about the distances at which pistols could be effectively fired at early on)


Correct, adjustable sight.
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