FIR stands for 'Fabbrica Italiana Ruote' (which might translate as 'Italian Wheel Factory'). The company was set up in Bergamo in 1956 by the Arrigoni brothers. As it name suggests, it specialized in the manufacture of bicycle rims and, later, complete bicycle wheels, especially wheels or the 'aero' pursuasion. FIR claims to be the first cycle-related company to have used carbon-fibre - in its Aru wheel in 1980.
FIR has a place on this web site because, during the melt down of the European cycle industry in the 1980s, it briefly sought to fortify its position by diversifying and offering a wider range of components. This included a number of different derailleurs. Strangely these were not simply rebadged models taken from major derailleur manufacturers, they appear to be FIR's very own designs.
FIR disappeared from the market in 2005, but were resuccitated in 2012 and seem to still be in business.