Personally for me i have seen 2 wheelock 7001t-24 alarms
I’ve seen a technical school up north that has Simplex 4050-80 light plates alongside Spectralert classics. One of the schools we take care of has Simplex 4037-1 flush mount horns that are still in place but have been disconnected.
The rarest I saw… That would probably go to an old convenience store in Southern France that had a bevy of Merlin Gerin SR-series sounders (that looked similar to the one I have) but smaller, with the occasional Roshni ROLP thrown in for good measure.
The call points were run down of the mill KACs rebadged by Esser.
Never saw the panel for this system but given the size of the store, a Type 4 panel wasn’t out of the question.
Second rarest system I’ve seen was comprised of Cerberus Guinard AT50MI call points (the vast majority having been replaced by Siemens KR-1 MCPs) and a 1970’s (!!!) Cerberus fire alarm panel (that was unfortunately partially gutted) tied to an addressable Siemens panel of some kind.
The last one is a bit painful as you know, Cerberus-Guinard equipment is extremely rare (it’s already rare in the rest of France) where I live, and a pre-Guinard buyout Cerberus panel from the '70ies, that’s a once-in-a-lifetime find.