They would be for 39/59 models. Remember before model numbers, the “Smith and Wesson 9mm” was what we now call the “pre-39”
I have never known a leather holster for a 39 not to fit a 5900, assuming hammer spurs on both models. The difference in the width of the frame would not be a significant enough amount of material to cause a leather holster not to fit.
Generally agree with all that. Specifically as to Bianchi, when the M59 appeared we changed all moulding of the M39 holsters to use the castings of the fatter pistol.
NOW: squidsix is understandably assuming what we think of in a leather holster, such as the Shadow:
soft (they're only cowhide after all). BUT: the M59 has a gigantic slide stop because the frame is much thicker right at that position vs the M39, for the bigger mag. So our 99A holster with its stiff metal shank DID NOT accept the new pistols; and to deal with that we installed a cutout through the lining to allow the slide stop to recess into it.
Pistol makers DO NOT take holsters -- or indeed any form of their transport or they would be designed differently from the get-go -- into consideration when designing their pistols. They do not consult with makers, they do not keep makers up to date, they do not warn makers.
So it was a surprise to us at Bianchi to learn the effects of the bigger S&W stop, the effects of S&W lengthening their 4" barrels on K frames etc. from 3-7/8" by 1/4" to beat the feared Saturday Night Special laws, the effects of Beretta increasing the size of the M92F's trigger guard by lengthening it until the M12 holsters no longer fit (even the Army wasn't told, so at first they blamed Bianchi for being the idiots when it was Beretta who was to blame).
Also bear in mind that most/nearly/all buyers think 'fits' means 'goes in and the strap snaps shut'. That's not 'fits'. That's 'snaps'. The pistol itself, maybe not so close as the M39 and M59, can go in and the strap snap up while the pistol itself rocks back and forth and up and down; and wears the finish for misalignment of the moulding. A maker absolutely does not consider that 'fitting' the holster.
Same holster; first with the N frame it was made for:
Next with the 1911 it was not made for:
We don't call that 'fits'.