Karl has custom cut first surface mirror for government contracts, for medical devices, for repair of cameras, for phone devices to use as an inspection tool, and other scientific uses. Obviously, he also cuts mirror for kaleidoscope makers as well. He has designed a mirror cutting system using a linear bearing and air pressure for straight and accurate cuts within a millimeter of tolerance. He makes sure that the desired size is as accurate in custom cutting as possible, and checks the size with a caliper before sending the mirror to the customer. He can hand cut squares or rectangles, but not circles, ovals, trapezoids, tapered mirrors, or other shapes, which is a frequent question. 
The first surface mirror that he uses is 1.25 mm thick and has a removable blue netto backing that can be pealed off to expose the side to be used in the application. He uses a sharp knife to separate the blue netto backing from the first surface mirror he just cut, so it remains to protect the cut mirror that will be used and then pealed by the customer. After he has custom cut the order for the customer, Karl takes particular care in packing the very breakable mirror so that it arrives safely. He uses a lot of foam packing materials to cushion the first surface mirror, which is more plentiful than the glass itself in many instances. He has shipped first surface mirror all over the world with great success, so don’t hesitate to inquire what he might be able to do for your project or process. https://www.kaleidoscopestoyou.com/front-surface-mirror-for-kaleidoscopes.html
Click here to see Karl Cutting Front Surface Mirror. https://youtu.be/h9PSNsWGNqc