Since the volume information of the tape is stored at the beginning of the
tape, the original contents of the tape would have been lost when a new
directory was written on the tape. Something you might try is to use the
INIT Tape Disk that comes with the Tape Backup 40SC software. Mount the
cartridge as a streaming device on the desktop, then attempt to use a
recovery utility, such as SUM, to recover the lost files.