There are countless variants of First Alert/BRK alarms floating around.
From what I can tell, their first detector was the SA76RS in the mid 70’s. There was also an early double sensor model, called the BRK model 3000, or the First Alert SA300. It had a clear test button and also a black protruding cone test button on the opposite side of the cover for the photo sensor. It also had a mechanical horn. Many BRK alarms were also sold under the Sears brand with different cover designs.
Then came the 1980’s with First Alert’s SA80FC and all those piezo alarms, like the 76RC and later the 67D. It also seems that there was an early SA67D (from the mid-late 80’s) with a thicker ring around the outside edge of the cover. The later models (starting from the early 90’s I believe) had a lower profile ring, giving the detector a smaller diameter. The later smaller 67D’s were often labeled as 83R, and I have several from the early 90’s with this 83R label.
And this isn’t even getting into their AC alarms…
Now for some pics!
Here is a First Alert SA300 from a 1983 AT&T smoke alarm monitoring ad. I wonder if this device is as good at picking up the tone from mechanical horns as piezo horns.
And this is the later (early-90’s) version of the SA67D. There was an earlier version that was almost identical except for a larger diameter ring on the outside edge of the cover.