The slide release is pressed and the slide retracted completely then pushed forward. Pulling the trigger fires the gun and releases the slide for reloading. On most models up to 1975, a second sear was installed that would drop the hammer as soon the gun went into battery if the trigger was in a depressed condition. Thus, holding the trigger down allowed the gun to fire the instant a new round is cycled into the chamber without requiring the trigger to be released; this feature was called "slam-fire". Otherwise, the Model 37 operates in much the same way as other pump-action shotguns; with the exception that, unlike most pump-action (and semi-automatic) long arms - which usually eject expended shells to one side, usually the right - the Model 37 ejects them downward, through the aforementioned loading/ejection port. This has made the Ithaca popular with left-handed users, who may fear hot shells being thrown at them by other guns. Selected versions S-prefix: were manufactured for a 1962 United States military contract. S-prefixed serial numbers ran from approximately 1,000 to 23,000 with "U.S." on the receiver and "P" proof markings on the barrel and receiver. The guns have a Parkerized finish with a barrel and plain stock with plastic butt plate and no sling swivels. A few later contracts produced smaller numbers of guns with sling swivels and serial numbers in the high 900,000 range. Some had "duckbill spreader" shot diverters for use by United States Navy SEALs. Others were fitted with a ventilated handguard and bayonet adapter. New bayonets were manufactured by General Cutlery, Inc. and Canada Arsenal, Ltd. Ultralite: an aluminium receiver variation. Deerslayer: a version with a shortened barrel and rifle-style sighting system. Turkeyslayer: a Synthetic stock (in black and camo pattern) version designed for turkey hunting. DSPS: for Deerslayer Police Special. A military and police version Stakeout: short version with a barrel and pistol grip stock. Because of its barrel length and overall length, this model is classified as a National Firearms Act 'any other weapon' 28 Gauge: 28 gauge model built on traditional size 28 gauge receiver. Defense: an affordable 12 or 20 gauge model built for home defense purposes. 18.5" barrel with 5-round capacity or 20" barrel with 8-round capacity. Essentially the same as the Model 37 M&P's used by military and police for many years. Users The Model 37 was used by the United States