Here are two B-17 engineering drawings related to its fuel strainers. The drawing of the strainer itself looks like your artifact, but the model called out in the drawings is 13960-3. Maybe it was replaced by 13961 late in the war, or maybe it's for another aircraft as previously mentioned.
I agree that looks like it is part of the C-4 fuel filter used on B-17 aircraft. There were several suppliers including Aero Supply who supplied the B-17 according to the parts catalog for the F model.
I think it most likely that the ASSEMBLY part number is 13960-3 and 13961 is the individual component in the major assembly. The -3 on 13960 would normally indicate the fourth version of the part.
The parts catalog specifically identifies the complete assembly as 13960-3