The shift to 3.5" disks occurred in 1983-1984. I recall the very initial Lisas shipped with a 5¼ disk, but switched to 3.5 later in 1983, the Mac shipped with 3

The shift to 3.5" disks occurred in 1983-1984. I recall the very initial Lisas shipped with a 5¼ disk, but switched to 3.5 later in 1983, the Mac shipped with 3.5 disks (but possibly only single-sided/400k). The Apple 2 line shifted to 3.5 disks with the 2gs around 1985-1986.