During World War II, the US military had a simultaneous need to put machine guns into combat service, and also a need to train new soldiers on the operation of those machine guns. Cutting up existing guns to make demonstration models reduced the number available for field use, and the solution was to contract for the manufacture of 200% scale fully functional (except for actually firing) cutaway models of the main service weapons. This is one such example of a Browning M1919A6 model (similar models of the M1 Garand, M1 Carbine, and M1918A2 BAR were also made).

Made by the Reflectone Corporation of Connecticut, these models are actually quite remarkably well made. Every part is a proper functioning copy of the real version, including springs reduced in strength to make the parts easy to operate, but allowing them to behave as a real gun would. With a model like this, a whole class of trainees could be instructed on various tasks relating to the gun, from basic loading and firing to complex malfunction clearance and complete detail stripping. They are typically relegated to hanging (inevitably covered in dust) from the ceilings of cluttered gun shops, but they are actually quite interesting and sophisticated devices.

Oh, and note that while this appears to be an M1919A4 without stock or bipod, it was actually made with the barrel profile of an A6, and the stock and bipod left off because they are mechanically irrelevant to training.