well... without checking the serial number... ( BTW... the gun is unfired ) I'm going to assume ... er maybe, that it's a later gun, & that they chambered it for an experimental 44 Bull Dog without the heal seated bullet, & they just never made a cartridge to fit the gun...
so I'm going to call it a "44 extra special" since the special is a shorter version of a longer cartridge ( or at least thats how it ended up )
we did run the barrel in one more turn, which gives me a .005" barrel cylinder gap, instead of a .033" gap as found... so I'll be loading my shortened 44 special cases with 160 grain cast lead bullets... velocities will still have to be tame, as it's definately a soft steel era gun...
I got a great deal on this gun in the 1st place, then to find it unfired, & in an easy to load unique chambering +++
thought I better attach a pic...