The usefulness of the 122-key "battleship" resulted in several Model M versions of the design, with this being the first. The Type I was a largely internal rework, swapping out the capacitive assembly for a membrane one and changing the bottom panel from metal to plastic. The rest of the design remained the same, including the dual-setting feet, and the top casing is fully compatible between the Model F and Model M versions. Like the F122 it replaced, the 24-key function key block was labelled either "Cmdxx" or "PFxx", with the most well-known host terminal being the IBM 3179 Color Display Station. These are also commonly referred to as the "M122" (although the later redesigns are also referred to as such), and thus "Type I" is used to help distinguish it from the others.