Sorry for kind of a triple post, I am working on my mystery siren map. Anyways, I'm confident that this is a mystery siren. It has a gigantic rain cover with no horns. It can't be a FS model, because it's upside down. It could possibly be a very heavily modified STH-10, but I highly doubt it. It does have that STH kind of mounting bracket, though...
https://earth.google.com/web/search/Cla ... cQAjoDCgEw