Great news…
I found the patent for the Simplex light/strobe plate.
http://www.google.com/patents/USD265802?dq=inassignee:Simplex+fire+alarm&ei=HLXrTuDBM4LX0QHHvIG0CQ
It said Annunciator (I don’t know why) when it’s supposed to be a Simplex light/strobe plate.