The Model Fs were IBM's second family of keyboards that were prevalent during the early to mid-1980s and succeeded the many large and tall beam spring keyboards that dominated the 1970s. They exclusively featured IBM's capacitive buckling springs switches, had well-armoured construction and also spawned a diverse number of variants for the various IBM terminals, personal computers and electronic typewriters sold in the first half of the '80s. The most well know Model F, the IBM Personal Computer Keyboard, played a huge role in the success of the original IBM PC and its terminal siblings are well sought after and regarded amongst keyboard enthusiasts. As with most IBM products of the time, Model Fs were instantly treated as a standard in which many IBM-compatible clone manufacturers tried to emulate. As such, Model Fs were responsible for the standardisation of the XT and AT layouts and protocols and played a role in the development of the layouts that would later become ANSI and ISO.
The Model Ms were IBM's third major family of keyboards that dominated from the mid-1980s to the mid-1990s and still in production via Unicomp. Essentially a cost-saving evolution of the Model F and its capacitive buckling springs, the average Model M with membrane buckling springs succeeded the Model Fs in all markets whilst retaining good reliability and build quality but also improving keyboard layouts significantly. The definitive Model M, the IBM Enhanced Keyboard, is quite possibly the most famous keyboard of all time and cemented the dominance of the ANSI and ISO keyboard layout standards that we still use today with only minor revision. Model Ms also spawned far more variants than previous generations, with Model M variants existing for the home PC, portable PC, educational PC, workstation, terminal, server, point of sale, typewriter and minor peripheral markets by the mid-'90s.
The ThinkPad keyboards started as a variant of the Model M that grew into its own diverse fourth major family of IBM keyboards. The original Model M6 and M6-1 ThinkPad keyboards set a high bar in the quality of portable computer keyboards upon their release, which started a pedigree that has survived to this day. Starting off with buckling rubber sleeve switches, ThinkPad keyboards have since become exclusively scissor-stabilised keyboards produced by a plethora of OEMs and are usually listed amongst the main selling points for IBM and Lenovo ThinkPads. By the 2010s, however, the original Model M6-derived line was replaced by the island/chiclet-style AccuType keyboards that whilst have vastly different layouts are still regarded as being amongst the most high-quality laptop keyboards still in production.
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