Canon EF-M mount
Canon's APS-C mirrorless mount, 2012 to 2023, killed off in favour of RF. Canon never licensed it, so every third-party lens was reverse-engineered and there were only six autofocus options in total from Sigma and Viltrox. Eight Canon lenses, eleven bodies, and then nothing. The 22mm f/2 pancake is the one to know: it was the last EF-M lens Canon had in stock and it now sells used for more than it cost new.
11 bodies and 20 lenses tracked. Lowest used prices pulled daily from the major used-gear sites.