You should also look for the process that created this first. . . Talk wth your storage management people and they may be able to tell you which job created this and what program actually created the dataset.
If the first method does not identify the "creator", suggest you dump the first few blocks of this dataset (in hex) and then dump the first few blocks of some other "backup" datasets and look for similarities.
If these are just straight data copies, it probably does not matter what created them. If they are DFDSS/adrdssu, or database backups, or anything written in some proprietary format, the content should be similar to other files created by the same process.
Hope this helps,