The 640 byte variant contains the text
(C) MPS-OPC 1991 v3.1
but the 654 byte one claims to be version 3.2. Not yet analyzed.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
A 469 byte version.
Probably the first version - 376 bytes.
This virus is structurally different, and belongs to a different family, as it only infects .EXE files, but it is probably written by the same authors.