The B56 was a long-stem version of the B44 triducer. It had a non-valve housing. The B56 was later replaced by the B66VL. The transducer was sold as either a 200kHz or 50/200kHz model.
The retaining clevis pin enters through the side of the threaded portion of the bronze housing in the same way as the B44.
The B56 used the #33-119 housing which is no longer available.