Simplex's pre-4208 DC fire alarm systems...

I had just recently found out the series of fire alarm panels Simplex offered in the late 1960s that used 24-VDC signals and battery backup instead of the standard AC-only setup we are used to. I learned this from this old Simplex “catalog” from 1967:
Simplex’s pre-4208 series of DC fire alarm panels was the 4211 series! (An actual panel would be something like the 4211A, very much like the 4246/7s, 4217s and 4208s and their numerous configurations.) Optional features included key reset switches, trouble buzzer/light and silencer, drill switch setup, smoke detection, fan relay and door release options. They were actually quite modular and expandable for their time, almost like 2001s were. They even had their own compatible annunciators:

(Model number 4331-6.)
As for signals, during this era they would have used Simplex 4041 horns, and there were DC 4030-series signals too, from what I’ve been told (they would’ve sounded like 90s Faraday electromechanical horns.)
I imagine back then, DC systems would have been more “rare” because I think they cost more than the AC systems did.

Additionally, the AC systems could come with master code, selective code, pre-signal and March Time options, along with the same options 4211s could have.
IIRC, these were discontinued some time in the early 1970s. The earliest the Simplex 4208 series was out was 1970 (I once saw an eBay auction for an AC-only 4208 panel dated from 1970), and could be just as customizable but unlike the AC 4246, 4247 or 4217 panels (the latter was a former IBM system) or the 4211, 4208s were available as AC or DC versions. Likewise the card-based 4207 panels that came out around 1975, then both discontinued in 1979 in favor of the 2100 and 2001 systems, after the discontinuation of the latter Simplex only made DC-output panels afterward.
Any comments?

Interesting discovery–do you know where the annunciator comes from?

It’s from the local registry of deeds/records. It was built in the late 1960s (there’s a serial date of 1968 on the annunciator), and the alarms are flush-mount Simplex 4041 horns, with Edwards 270-SPO pulls.