M2 – Stuart light tank
M3 – Lee (Grant in UK service)
M4 – Sherman
M5 – Stuart (again, uprated M2)
M6 – heavy tank never really went into mass production
M7 – Priest SPG
M8 – howitzer on an M2/M5 chassis
M9 – prototype only
M10 – tank destroyer, Achilles in British service
M2 – Stuart light tank
M3 – Lee (Grant in UK service)
M4 – Sherman
M5 – Stuart (again, uprated M2)
M6 – heavy tank never really went into mass production
M7 – Priest SPG
M8 – howitzer on an M2/M5 chassis
M9 – prototype only
M10 – tank destroyer, Achilles in British service
I was being facetious, the Abrams is an M1, there is no M11.