The Model 44 Carbine was adopted in 1911, the 44th year of the reign of the Emperor Meiji. Hence the Model 44 designation.
The following production chart is from the February, 2001, issue of the Military Rifle Journal, page 33.
Picture number M44010 (courtesy of Shannon Zeigler) Right side of the Model 44 carbine.
Picture number M44020 (courtesy of Shannon Zeigler) Left side of the Model 44 carbine. Note the side mounted swivels for cavalry use.