While I'm unaware of any way to trace an output back to its original XPJ. I'm thinking that perhaps the easiest way to determine this would be to compare date/time stamps. Just look at the output folders for each of the copies of the projects.
Thanks for the reply, Rick. I tried that before posting here and to my dismay it seems as though the project it came from may be under a unique or unrelated name (there are probably 50 project files on this machine - lol).
And all fifty are using the same project name? Perhaps by existing in 50 different folders?
There are ways to rebuild your project from just the WebHelp output on William Van Weeden's site: https://www.wvanweelden.eu/product-category/recovery-script
If you don't want to go that route, another avenue that will get you to the same place depends upon whether you can see the !SSL! folders for each of those 50 project files. Are each of those 50 project files are stored with the supporting HTML, CSS, & other project files within their own folder - meaning 50 project files in 50 project folder? If they are, do they have the !SSL! directory for WebHelp?
If they have a !SSL! folder, skip to step 2, else, continue with this step. Write a DOS batch file with a DIR command to get the full path to each of the .xpj files. Then, use find & replace actions in a text file editor to add the syntax necessary to recompile each project and specify a separate output directory, preferably named with a naming convention that makes it easy to link between the .xpj file name and the the output directory. If you are unfamiliar with how to do that, I would refer you to Peter Grainge website: Command Line Generation
Step 2 would be to use Search My Files (SMF is freeware software that I use frequently) to identify by file size and file name the base folder you are comparing to with one the !SSL! folders. By specifying those two parameters, SMF will get you in the ballpark quickly.
Sounds like a fun project...