[Sold by Manufacturer]. Mounted AN glass 35 mm slide in GEPE art 6013 Full Frame frame with metal mask. The opening is exactly 24x36 mm vs 23x35 in any other mounts. That allows to fine tune scanning rig to capture full 24x36 mm frame. This is  High Resolution 35 mm Test Target (Test Chart) for Camera scanning -  Fit Valoi 360 , VALOI Easy 120, Negative Supply, Digitaliza+, vintage Canon, Nikon slide duplicators.

Vlads Test Target is a tool designed specifically for camera scanning that helps ensure critical focus, especially in the corners of your scans
The chart contains multiple USAF 1951 patterns strategically located across the frame that can help you gauge the quality and capability of your lens, allowing you to make more informed decisions when selecting equipment for film digitizing. 
The Siemens stars facilitate effective visual control over film plane alignment relative to the camera sensor. Along with "focus peaking" feature they make initial camera scanning setup a breeze.
This Test chart helps align camera vs film properly and maintain alignment over course of scanning session.
Over last five years Vlads Test Target (test chart, sharpness checker) became the gold standard of quality and affordability for camera scanning, film digitizing community and service labs across the globe.
Users of classic flatbed and film scanners find the test target the ideal mean to test the tuning of their equipment. 
Target native resolution is 110 lp/mm - fat exceeding the resolution of digital cameras and scanners. 
• For 35 mm strips, medium format (6x7 & 6x9)  and  4x5" and slides - see other listings. 
• Make sure to buy from manufacturer [seller vladimirs] to get 2 year wear and tear warranty on your purchases.