The 1926 Paasche Catalog page for the "Type M" and "Type ML." They were the 20's versions of the "V" and "VL."  Note that the "Type ML" is a side feed; the next version, the "Type MSL" was changed to the bottom feed like the current "VL." Also note the little round button in front of the trigger. It has an eccentric hole and is used to limit the forward progress of the trigger thus keeping the needle and the tip at the same opening for repeatability.