Hi everyone,
I've been playing around with a kit of mine trying to finish it for pics, but the results of one of my items were so good I decided to post it a bit early.
Some of you might be aware on the periphery that the hard drive disk in your computer is likely either glass or aluminum with a magnetic coating. These platters spin at outrageous speeds and can not deform in any meaningful way. Thus they are very resilient, flat, and almost perfectly reflective because of this.
I had a stack of old Jaz disks (Iomega) laying around and realized that they might make a good signal mirror. You can pick up a Jaz disk on eBay for pretty cheap - it really doesn't matter what shape it's in unless it's had a head crash which may scratch the surface. Each Jaz disk has 2 platters, and you can get them as cheap as a buck. One could use an old 3.5" or 2.5" hard drive in much the same manner.
The disk platter works as a great signal mirror. I tested it side by side against a similarly sized Ultimate Survival 2"x3" mirror.
The Jaz signal was much brighter and less "spread out" by the time it hit the target (my porch siding - the Jaz is on the left) 10-12m away.
Keep in mind that the siding is dark gray and absorbs a lot of the light. Reflected against a shiny or white surface, it's actually difficult to look at. It can light up a car's reflectors from a block away without ANY difficulty in broad daylight. I find it to be at least twice as bright as the US 2x3" and I've carried it in my pocket with other metallic objects without much damage. It does not scratch easily, however I would recommend you get a "badge holder" available in any super-mart or office store. The thin pieces of clear plastic make a decent carry and protector for the mirror and they allow it to "signal" even if you are unconscious.
Cost of Jaz disk - $1-2 if you can pick it up locally (no shipping). Cost of protectors: $1.50 for a pack of 20 Wal-Mart specials. Super flat, very thin, and highly portable.