AUTOCHOP
From Just Solve the File Format Problem
AUTOCHOP is a file splitting utility for DOS. It was developed by Randy Langer and MicroSphere Technology, and distributed as shareware.
Format details
Fragments are given filename extensions consisting of a number sign (#), followed by two digits. For example, a file named "EXAMPLE.DAT" will be split into fragments named "EXAMPLE.#00", "EXAMPLE.#01", etc.
Each fragment starts with a header. More research is needed to figure out the header format.