There is only one file type that uses the .T65 extension:
PageMaker Template File
A T65 file is a template created for PageMaker 6.0, a page layout designing and formatting application. It contains a character set template for identifying key strokes for ASCII characters available in most fonts. T65 files are referenced by each version of PageMaker 6.0 and earlier.
T65 files can be found in your "Extras" folder in your PageMaker folder.
Examples of keystroke and character data held in a T65 character set:
0172 - ¬
0174 - ®
CS+6 - §
PageMaker was originally introduced in 1985 by Aldus but acquired in 1994 by Adobe. In 2004, Adobe stopped development of PageMaker replaced the program with InDesign. The Mac version of PageMaker will only run on OS 9 or earlier whereas the Windows version of PageMaker will run on XP or earlier.
NOTE: T65 files were replaced by the .PMT PageMaker file in PageMaker 7.0.
charset.t65 - The common filename of the character set referenced by PageMaker to identify keystroke functions.
Updated: December 26, 2017