A Wonder Nine is a semi-automatic pistol chambered in 9×19mm Parabellum with a staggered column magazine and a double-action trigger for at least the first shot.
During the 90s most American police departments were still using revolvers, with the majority chambered in either .38 Special or .357 Magnum.
The simplicity of being able to fire the first shot just by pulling the trigger (a prominent feature of double-action revolvers), larger ammunition capacity, and faster reloading of ammunition with the use of box magazines are the "wonderful" features of a semi-automatic pistol.
Examples include the Heckler & Koch VP70 (1970), Smith & Wesson Model 59 (1971[1] [2]), CZ-75 (1975), Star Model 28 (1975), Beretta 92 (1976), Steyr GB (1981), Glock 17 (1982), FN HP DA (1982), SIG Sauer P226 (1984), Ruger P85 (1985), Walther P88 (1988), IWI Jericho 941 (1990), Vektor SP1 (1992), Heckler & Koch USP (1993), Bersa Thunder 9 (1994), Walther P99 (1997), and Steyr M (1999).