That’s awesome dude! The SS749s are also one of the alarms that I want to find but just while homesearching as they are extremely rare to find in online marketplaces.
2 rarities I bought off eBay recently, a ESL 906-2, very hard to find especially on eBay. The other is a rare Sunbeam Centurion 45-31, a GuardION FB-1 rebrand with a test button.
Here is something I found in a condo of all places, a BRK model SS749AC or SS749ACS. And yes, it’s actually still operating as you can see the red power LED that is on.
Yeah that’s my mistake, at the time that I sent it to the forums I didn’t watch the stream where you found it, and I randomly bumped into the house that had it.
Is this a smoke alarm? It looks like it has some sort of button above the cutouts and a dark spot towards the bottom that looks like an operation indicator. It also does sort of look like a chimebox for a doorbell.