+1 to Tony.
at various evolutions, my kit has a similar setup with an blank CD that is silver shiny on both sides. Part of my kit is to include a lanyard through the center hole, for example to hang the reflective mirror around my neck, or the outside of my backpack, or to hang off a sunny tree branch twirling in the breeze to strobe signal for help.
Other elaborate combinations would be to use the LED headlamp strobe blink features to reflect off the disc, to double to signaling potential at night.
My CD cracked and started to separate layers after 5 years of being stored in my "oh_ śh . ĩt _kit" never got to use it, neither for fun or for emergency - lucky I suppose.
A lot safer than starting a forest fire to get rescue attention - which is the popular approach these days in the San Bernardino National Forest, according to the rescue volunteers.
This is repurposing old technology trash, and giving it a second life and a second purpose, without having to buy an expensive gadget that does the same function.