I picked up a signal with several 27's in it, how many versions of the 27 did they produce, and which one is oldest?
One has no markings at all on the edge.
Several say: "Horni Signal Mfg. Company New York City" #27
Several more say: "Horni Signal Mfg. Company New York City" Kopp NO. 27.
Pic's when I get home.