This is ober 100 alarms ranging from 1999 all the way through 1963!
Ive
been collecting since 2018.
Welcome to the forums! Wow that’s a lot…excellent collection there! You’ve certainly single-handedly helped preserve many detectors that would have been unceremoniously thrown in the trash! (& thus been forgotten by history!)
Interesting how going by the layout you have there (provided it’s in chronological/historical order of course) detectors started off mainly round, then were pretty much always square in the 70s, & then went back to round (perhaps that was from manufacturers trying to get the public interested in buying smoke detectors with a new gimmick, in this case a new shape (which they might have also advertised as blending in better with home decor than round detectors).