Zim-Gar was the brand name of Gar-Zim Musical Instruments, an import and distribution company located in Brooklyn, New York. It was run by Larry Zimmerman and his wife. At one point, it may have been known as the American Musical Instrument Corporation before Zimmerman took on a partner (Mr. Garfield) in the Garfield Zimmerman Music Company. This was eventually shortened to Gar-Zim Musical Instruments. There were Zim-Gar branded guitars, ukuleles, banjos, mandolins as well as percussion instruments. Some of the guitars were made in Japan by the likes of Teisco.
Source: National Music Museum - Gar-Zim Musical Instruments (5 January 2022)