Quick I think I figured it out. I think I have an SB1 Frame.
Look at the differences in the holes for the firing pins.
Notice the differences in the hinge area. One has been tooled, and the other lookes cast.
Also notice the finish properties inside the receiver - one looks cast, the other tooled.
This is NOT an SB2 receiver.
In all pics the Left - receiver that had the .270, right - 45-70/44mag receiver.