Atari floppy drives were known for its slow operation. As a result, third parties rushed to create solutions to improve the drives as the company wasn't. One of them was Irata (Atari spelled backwards) accelerator board, which conveniently removed the original ROM from the drive and replaced the 6507 with a full 6502. Being considered a permanent mod, the case of modded units is often perforated in order to place a switch.
I fear my unit was not an original Irata board, but a clone and as a result it has hand-made curve traces and no markings, so identification was made visually by comparing Atari 1050 third-party internal expansions with the board in hand.
Disclaimer (1): The process was non-aggressive, so it was not dissassembled at all to study it. Therefore some traces may reamin undetected under the integrated circuits and not documented. Use it at your own risk.
Disclaimer (2): This is a reverse-engineering work for study, repair and preservation purposes. The license only apply to the documents resulting from foresaid study and does not claim property over the original design or firmware.