Seeing your photos, I let myself dive into my doc and my memories did not deceive me. I do not know how to give an exact complete identification, but I know how to give leads for research
First, the type of welded suspension system is very similar to WWII Russian bombs
Second, the empennage attachment system is also similar to a Russian system from the same era (on pic, fixation of an empennage of FAB-50 STsch, 1944)
Third, if your dimension of 31 inches (78,74cm) is indeed the total length, including the empennage, we cannot estimate the weight of the bomb at more than 50 kg.
Yoda