While relatively fragile and heavy, glass signal mirrors are the gold standard for reflectivity, against which we measure others. Many still prefer them to even the best plastic signal mirrors. There are two types of laminated glass signal mirrors commonly available in the U.S., ones made in the U.S. in conformance to the old mil-spec MIL-M-18371E by S.I. Howard Glass and those made in Japan for Vector 1 and which have been distributed under a few brands, Coghlan's being the most commonly available.
Recently an associate who collects signal mirrors and who is a student of their history emailed me about a bunch of phony glass signal mirrors that have suddenly hit the market. They appear to be poorly constructed copies of the Vector 1 signal mirrors (though they may well have copied some other similar mirror available overseas) with the two pieces of glass often misaligned and a much less substantial aluminum rivet in the lanyard hole (the S.I. Howard mil-spec mirrors have no rivet). Beyond the lesser quality construction, and of much more concern, these fakes appear to have a mesh retro-reflective aimer, but it is nothing more than a printed imitation done in silver ink. It is NOT retro-reflective and it does not work (this isn't the first time; for a number of years Skyblazer sold a plastic signal mirror with a similar fake aimer). In my opinion, the only apparent function of the fake mesh is to fool people into thinking they are buying a mirror with a genuine retro-reflective one-handed aimer.
The images below show the differences between the real retro-reflective aimers, which are created by gluing tiny glass beads to real mesh, and the printed fake (left to right: S.I. Howard, Vector 1, Printed fake).
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