http://www.rockislandauction.com/viewitem/aid/65/lid/1681

The Menz Liliput is one of the smallest functional firearms ever put into mass production. It was offered in 4.25mm (.17 caliber) in addition to the more popular .25ACP and .32ACP. The 4.25mm cartridge is used generated about 17 foot pounds of muzzle energy - trivial by most pistol standards, but still several times that of the even tinier 2.7mm Kolibri.

These pistols were made in the 1920s - some sources say from 1920 to 1927, but what I have found seems to point towards a commercial introduction in 1925.