Triple Locks, serial # 2 and #9,both formerly in my possession, ( yes, #9, Number 09 is a different gun) are both chambered in .45 S&W Special. No caliber markings on either gun. I believe S&W labeled a quantity of boxes with the end label that says "S&W .45 Special" in the anticipation that the cartridge & revolvers would be come cataloged items, as more of such boxes have turned up over the years, than the guns. Ed.