WELCOME~ here is some info I dug up.
The Marlin Firearms Co. has been in the .22 autoloader business since 1931. However, until 1959 none of the New Haven, Connecticut, firm’s semi-automatic .22s could be called a resounding success. That changed in 1959 with the introduction of the side-ejecting, blowback-operated Model 99. Designed by Marlin’s Ewald Nichol, the Model 99 employed a round 22” barrel and featured an 18-.22 LR-round-capacity tubular magazine mounted under its barrel. The top of the receiver was drilled and tapped for a scope base and sights were a hooded ramp front and an open rear. The Model 99, according to the late Col. William S. Brophy in Marlin Firearms, was offered only until 1961. The 99, however, served as the basis for an entire series of autoloaders that are still well represented in the company’s annual sales nearly 40 years later.
The Monte Carlo walnut-stocked Marlin 99DL with a gold-plated trigger and gold-tone trigger guard was introduced in 1960, and it featured a buttplate and grip cap with white line spacers. Later a leather sling was standard on the 99DL before it was dropped from the line in 1964. The 99C was introduced in 1961 and differed from the 99 in that it employed Marlin’s then-new Micro-Groove rifling and had a gold-tone trigger blade. The 99C had its receiver grooved for tip-off scope mounts in 1964. Initially supplied with an uncheckered walnut stock, the 99C had impressed checkering added in 1971, and the checkering pattern was changed again at least twice more before the rifle was discontinued in 1978. A deluxe version of the 99C with an American walnut stock, the Model 990, was offered from 1979-1987.
The Glenfield Model 60G—essentially the same rifle as the Model 99C except with a birch rather than walnut stock—was made from 1960 to 1965. The Glenfield name was used on Marlin-made guns intended for sale to mass-merchandisers. The rifle was later dubbed the Glenfield Model 60, and it continued to be offered with slight cosmetic changes from 1966 to 1982. In 1968, a Model 65 Glenfield that was essentially identical to the Model 60 with the exception of a brass exterior magazine tube was made for Oklahoma Tire & Supply Co. Private brand variants of the Model 60 were also made for Montgomery Ward, Coast to Coast Stores and Cotter & Company.
Marlin stopped using the Glenfield name altogether in 1983, and the Glenfield Model 60 became the Marlin Model 60. Initial Marlin variants did not have checkering on their birch stocks. In 1985 all of Marlin’s tubular-magazine-fed semi-automatics received a bolt hold-open that locked the bolt open after the last round in the magazine was fired and that could be used to manually lock the bolt open.
An 18”-barreled variant with an appropriately shortened 14-round-capacity magazine tube and an overall length of only 371⁄2”, the Model 75C, was last cataloged in 1991. A laminated stock, rubber buttpad, gold-tone trigger and sling swivels were the hallmarks of the Model 990L, first offered in 1992. Concurrent with the 990L’s introduction was the reduction of the magazine tube’s length and capacity to 14 rounds. The Model 60SS was introduced in 1993 and had a laminated stock, a stainless steel breech-bolt, barrel and outer magazine tube while most of the other parts were nickel-plated. Impressed checkering in a diamond pattern was added to the Model 60 in the 1995 catalog.
According to Marlin, as of August 1997, autoloading .22s with tubular magazines based on the Model 99 had been made to the tune of some 6,200,000 rifles—an accomplishment that few other sporting arms can match.