If you want to know about glass signal mirrors and/or retroreflective mesh signal mirror aimers,
see this excellent article by Doug Ritter, the founder of this web site:

"Warning: Phony Glass Signal Mirrors", by Doug Ritter, on Equipped to Survive

Doug's article covers:

- How retroreflective signal mirror aimers work
- How to tell a real retroreflective aimer from a phony one
- How to use a retroreflective signal mirror aimer
- Where to buy 2"x3" and 3"x5" glass signal mirrors with retroreflective aimers.
- The original patent on the retroreflective mesh aimer
- The US Govt. MIL-M-18371E specification for glass signal mirrors

There are quite a few official US Government photographs of MIL-M-18371E mirrors in action. Some examples:

(1) 2"x3" MIL-M-18371E mirror in use, with notes
(2) Close look (2000x3100 pixels) of 2"x3" MIL-M-18371E in use
(3) 3"x5" MIL-M-18371E mirror in use, with notes
(4) Close look (2068x1504 pixels) at 3"x5" MIL-M-18371E in use


[Disclosure: I provided Doug with references and illustrations for his article.]