The Lettet Forsøgs-maskinpistol was a variant of the Suomi KP/-31 submachine gun of Finnish origin adapted for Danish service. It was made from stainless steel with a tubular buttstock and a distinctive ball-shaped wooden foregrip intended to improve ergomomic flexibility for the user when handling the weapon. This unique feature was later found pointless and somewhat expensive for mass production and therefore manufactured in its original form as the M/41 submachine gun.