This from Walt Snyder..." Introduced in 1970, the model 51 was a gas operated semi-automatic shotgun designed by the late James Tollinger. By 1971, the Model 51 was available in several 12-guage configurations, including standard and deluxe grades and trap and skeet grades with vent ribbed barrels. Retail prices varied from $179.95 to $ 245.95. Deerslayer and Magnum Models were introduced in 1973. Twenty-guage options were available by 1973. All model 51 production was suspended in 1987."
It was an extremly reliable gun unfortunately thrown into head to head competition with the the Remington 1100. It's fate was preordained.
'Lonzo