Acorn high density 3 1/2" disk
From Just Solve the File Format Problem
The Acorn high density 3 1/2" disk was used with Acorn computers, a line of computers from the UK in the 1970s through 1990s, which included the popular BBC microcomputer, and eventually led to RISC OS. It succeeded the Acorn double density 3 1/2" disk.
The disks were double sided, with 80 tracks per side and 10 sectors of 1024 bytes, for a total capacity of 1600 kilobytes respectively. MFM encoding was used.
The ADFS (Advanced Disc Filing System) was used as the file system, and BBC BASIC tokenized files were among the file types stored.