Gary is a custom logic IC which implements address decoding, default bus timing (AS/DTACK) and some floppy drive logic.
There are apparently bugs in the earliest Toshiba Gary ICs. These start with TC17xxxxAP and have 87 date codes.
A new post from David Haynie in 1993 (link unknown unfortunately, they didn’t post the article ID or the newsgroup name):
The MOS 5719 chips are … less buggy? Need to go figure that out and document things here.