Sharp 2.5-inch floppy disk
From Just Solve the File Format Problem
The Sharp 2.5-inch floppy disk (CE-1650F) was one of several odd-sized floppy formats that never caught on. It was 2 1/2 inches in size. It was used with some models of Sharp pocket computers that used the BASIC language. The capacity was 128 KB on double-sided disks with 16 tracks of 8 sectors with 512 bytes per sector, using GCR encoding.
