Windows Phone Xap Archive
: Part of the official Windows Phone 8.1 SDK, this tool allows for direct manual deployment of XAP files to a connected device.
The signature is stored in a [Content_Types].xml file and a META-INF folder containing a .psm file (package signature manifest). Windows Phone validates the signature during installation and every time the app launches (integrity check). windows phone xap archive
Many apps were removed from the store even before it closed; archives often contain versions of software that haven't been seen in over a decade. Mechanics of Survival: Sideloading and Deployment : Part of the official Windows Phone 8
If you want, I can generate a preservation template (checklist + metadata fields) you can use to catalog a collection of XAP files. windows phone xap archive