The famous Suomi submachine gun or machine carbine was designed to be an "everlasting" piece of equipment. Broken or worn-out parts like extractors, barrels, breech-bolts, recoil springs and wooden stocks were easy to replace. Receiver and jacket were truly durable parts, and - with the exception of some springs and pins - the small pieces of trigger mechanism did not easily wear out. The very first prototype of the SUOMI gun was made by a young Finnish Army armorer, AIMO JOHANNES LAHTI (1896-1970) in 1920 or 1921. The caliber was .32 A.C.P. or 7.65 mm Browning. The gun was 30 centimeters (11.8 inches) long. This "machine pistol" was a very reliable gun but the .32 Auto cartridge was too weak for "serious military use" and the cyclic rate of fire was presumably too high.