A brief Remington autoloading shotgun primer...
The model 11 was a hump-back Browning clone, and was made from 1905-1949. The 11-48 replaced it in that year. Both are recoil operated. Remington's first gas operated autoloader was the model 58, made from 1956-1964. this, and the 11-48 were phased out in favor of the model 1100, which came out in 1963. In 1987 they "improved" the 1100 and called it the, you guessed it, the 11-87.