The so-called "blue switch" Model F terminal keyboards were a series of five keyboards originally for the IBM 3178 Display Station released in Q1 1983 and later for the IBM 3104 Display Terminal. Characterised by their blue switch used for toggling the terminal's display between mixed-case or uppercase-only characters, these Model Fs featured a heavily modified XT-like layout with two or three function banks depending on SKU. These keyboards are known for sporting a solenoid, something relatively unusual for Model F keyboards.
