Epson GT-6500 EN - Manual (Page 101)

For a more detailed explanation on using the ESC I command and the
contents of the returned data block, see Chapter 2 and Appendix B.
The length of the data block varies depending on the scanner model.
The host computer should check the byte counter.
Contents of the ESC I (identity) data block
The contents of the ESC I data block for each scanner model are
listed in Appendix B.
Command Reference 3-7