The shiner itself is ultra thin and made from polished stainless steel and is set into the match box at an angle to give its user the easiest of peeks. Can be used to peek the top card or the bottom card in a deck while dealing. This does take a bit of practice but once the skill is learned its well worth it.
These will be a very limited edition and I am only going to make about 50 of these do to the time required to make each one which is considerable and a bit more costly than one would think. The stainless used to craft these is 26Cr-1Mo ferritic stainless steel chosen for its reflective ability when the surface is polished. This type of stainless will attract a magnet but that should not be a problem for those wearing pk rings.
This type of clandestine shiner was common in back room gambling games around the turn of the 19th century and was used from time to time on riverboats during a previous time period. This type of shiner is rather rare and seems to only survive in a few private collection and some old picture can be found in some of the early books on crooked gambling. Outside of that the device is seldom seen.
In the attached photo you will see the device from two angles front and back. Although the performers view of the device in action is not the best in the photo, the basic idea can still be seen as to how the device works.
One more thought, while these devices are seldom used by gamblers these days they are perfect for magicians who do close up as there are thousands of tricks that can be done with ordinary wooden matches which will give you a perfect excuse to bring for the box of matches with its hidden gaff that can be used later in the close up show.