An xy3 file extension is related to the XYWrite III document format. Probably obsolete file format.
XY3 file extension - XYWrite III document
What is xy3 file? How to open xy3 files?
File type specification:
The xy3 file extension is associated with The XYWrite III document - a text document created by version 3 of XYWrite.
Most likely some old format without support. No further information could be found.
This xy3 file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.