> XTND was a document import/export system developed by Claris for
> their products on the Apple Macintosh. Products supporting XTND
> placed an additional popup menu in the open and save dialogs,
> allowing users to read and write documents of any supported format.
> The name is a four-letter contraction of extend, the Mac using four-
> letter identifiers in its system resource files.
>
> XTND was first introduced on some of Claris' "II" releases --
> MacWrite II, FileMaker II and MacDraw II. The system proved popular
> and became a major selling point for Claris products, which were
> otherwise considered somewhat "low end". The system was soon used by
> a number of other products as well, and became fairly common during
> the early 1990s.
>
> Around 1990/91 Claris gave the system to Apple, who eventually re-
> branded it as a basic part of the Mac OS known as the Translation
> Manager. They also added Macintosh Easy Open which offered to open
> unknown documents using software installed on the machine and
> converting it using XTND. A developer's guide, XTND Programmer's
> Guide, was published in 1991 along with the XTND Developer's Kit
> 1.3, which was placed on their FTP site. XTND broke on the Power
> Macs, but an extension-to-the-extension released in 1993 fixed that
> for a time. By the 1995/96 time frame it appears Apple had already
> abandoned the entire system.
>


\- Wikipedia, [XTND][1]

Download contains disk image of XTND Developer's Kit 1.3

Compatibility
Architecture: PPC

  [1]: https://en.wikipedia.org/wiki/XTND