looks to me like a variation of a model II,
Spotmeter | My Pentax
Big thing that caught my eye is that it takes a Mercury battery, which you can't get anymore, need to find a silver cell variant, and the circuitry on old meters does not like the different power curves. Inconsistent results across the life of the battery.
If you really want a spot meter to use, get a V, VI or the digital, they all took silver cells, which are easy to find.
That name plate on it looks funky too, almost like it's been 3D printed, all the others of that vintage I can see the tops of seem to have printed foil names on the top of them.
Could be rare because someone made only one name plate,