A couple things about the 37....
The design is by John Moses Browning. Originally brought out by Remington as the Model 17 in 20 gauge, Ithaca brought their version out in 1937 after the patents expired.
Like all JMB designs,the 37 is overbuilt.Super rugged but light for the load, they last darn near forever. They shuck very smoothly and fast.
The first martial use of the 37 seems to have been on Guadacanal in WWII. By the time of the Nam Mess, 37s often served point men as good, reliable jungle weapons. Fast, reliable,and the load from the bottom feature meant one less way for mud and detritus to enter the receiver.
By that time, the Deerslayer variant had been introduced. This was the first commercial model slug gun, using a tight bore that was basically full choke all the way. This proved accurate and served well for buck also. The open sights and effectiveness sold lots of 37s.
The design,like many of JMB's,requires tight tolerances and lots of machining. The 37 is not the cheapest pumpgun around. Even with the steel receiver, though it is one of the lightest.
Quality has remained good over the years though some 80s examples made during a time the company went into bankruptcy were rougher.
In the US,$300 will often get you a near new 37 that will last for generations.