I remember seeing a photo of a rotating Scream Master siren in a newspaper dated around 1952 to 1956. This siren had two heads, like a 550-DHTT, but had a 20hp motor and had an output of 125 decibels at a 100 ft.
I scoured Google, the entire forum and also on the ARS subreddit, but couldn't find the photo.
Source: https://www.airraidsirens.net/forums/vi ... er#p181112