The combo movement first appeared in 1975, as LED digital watches were gaining traction. Beltime also used the term “combo” at that time for watches that combined LED and LCD displays. Heuer's Chronosplit also used both technologies, with the LED used for the chronograph function.
Zenith was one of the first to market with a watch that used hands for hour and minutes and a digital LED array for the seconds. Their Time Command was a futuristic rectangular watch with a pushbutton LED display at 5 00 or 6 00. A similar module was created by Microma in 1978, which used continually running LCD below the dial.
In 1984, ESA launched a range of thin combo movements, including the Flatline Combo Cal. 958.331, which measured just 2.0 mm thick, the Combo Dichroic Cal. 988.331, which was 3.0 mm thick including the dial, and the Combo Delirium Cal. 999.331, which allowed a 2.98 mm thick watch.