OpenDocument Drawing
From Just Solve the File Format Problem
OpenDocument Drawing (also known as ODF Drawing, OpenDocument Graphics, or ODG) is a vector graphics format intended for use with office applications. See OpenDocument for more information.
Disambiguation
OpenDocument Drawing is distinct from the somewhat-mysterious format named OpenDocument Image.
Identification
OpenDocument Drawing files usually use ZIP as a container format. In that case, the ASCII string "application/vnd.oasis.opendocument.graphics
" appears at offset 38.