I found a really weird looking siren, that shows up as "mystery thing" on the Nebraska siren map. It does seem to have a chopper, so I'm wondering what this siren is:
https://earth.google.com/web/@41.497722 ... IAI6AwoBMA
I don't know if it's a Model A or another smaller siren, the chopper seems way too big for anything like this.
EDIT: I don't think it's a Sentry F siren as well. There's too many chopper ports for it to be one.