ACB (compressed archive)
From Just Solve the File Format Problem
ACB is a compressed archive utility for DOS, and its associated file format. It was developed by George Buyanovsky, and released as shareware.
It appears to have a file patching feature, which it calls "trainable channel mode".
Identification
Based on IDArc and other evidence, the byte at offset 1 is between 0x80 and 0x84 inclusive, and the byte at offset 3 is 0x00.
