It is the back half of an M9A1 US mid-to-late WW2 Bazooka . Replaced the M1series and was the model for the post WW2 M20 3.5-inch . It is 2.36 inch .
The shoulder stock bracket is awary on this . With the rear , rocket holding clamp at 12 oclock , bring the shoulder piece to 6 oclock , resting midway between the sight bracket and the front tube retaining
latch . The front grip / trigger assembly attached to that rusty / discolored area in front off that retaining latch and also between the latch and sight bracket in the rotational alignment .
For packing , the front tube had a hook that went into the loop near the rear and a box deal at the front that engauged the latch .
For use , the front tube was detached , that little tiny lever at the front of the rear section rotated open , the front section's splines placed into the rear sections splines , twist to lock , then release the little lever to lock in ( friction fit ) .
My live one cost me 3K back in '07 ( mint condition ) . I've turned down 5K . Yours would be worth whatever someone would be willing to pay . The trigger group and sight would be easy , the plate the grip attaches to would have to be made unless you luck out . The front half would be the hardest . If you were able to make it a complete non functional dummy , you might get a grand .
Chris