I’m not sure either, I do know HOR had odd model numbers and names that did not match up with what they were calling them (this one being a “Model 50” but it was called Super Si-Rex in advertisements...
I did some research last night and found that Ohio had about 5 or 6 single headed Sirex’s at one time, Lake County had three according to a CD matching funds document, and the only others I know off the top of my head are this one, and the one in North Canton (which was purchased in 1951). I believe the one in Hamilton went up around 1954 if I remember right. I’m not sure if all the single headed units were dual toned or not but I know this one and the one in North Canton both were based on pictures of the North Canton one which were in local news articles and comparing those photos with this unit.
The towers they were mounted on for roof mounting had to be constructed by whoever was installing them. North Canton’s in particular did not go up for three years after they got that siren because they did not have the necessary equipment to construct the tower and platform required for roof mounting.