/mobile/Library/Caches/com.apple.Pasteboard/.* - This directory will contain one or more other directories with a naming convention that appears to be hash values without file extensions.  The files without extensions can be anything the user has copied.  The file can simply be ASCII text if a string was copied, or the file can be a photo or video if the user copied those. 

An example of the copy/paste is shown below.  Jared Barnhart provided these examples.

Copying a photo from the Photos app of Tito’s and a soda with lime in La Jolla - Torrey Pines (see image, following page). When the photo was copied, a directory was created and the copied file was written into it. 

The /private/var/mobile/Library/Caches/com.apple.pasteboard/directory and files created when the photo was copied were then pulled from the device. 

This file without an extension is a version of the image file that was copied.  

The actual image file that was copied was IMG_0036.HEIC and the file size differs from the copied file and the hashes do not match.  

Within this directory the Manifest.plist contains the time the item was copied (NS.time key / Mac Absolute Epoch) and the application bundle the data was copied from - “Photos”.