GEOS Convert
From Just Solve the File Format Problem
Convert is an archiving format associated with the Convert utility included with some versions of the GEOS OS for the Commodore 64. GEOS "files" are not ordinary files, so Convert and similar formats are sometimes used to transfer them to other platforms.
Convert can be used with both GEOS VLIR and GEOS Sequential files.
There is also an Atari version of the format, which is reported to be quite different from the C64 version.