First off, the sirens themselves:
We have a name, and it's what most of us have been calling them: Custer Electric Sirens. Each unit is comprised of an isolated speaker cluster, controller, solar panel, and battery at the top of a pole. Every unit is 200W except for the Knightstown double-speaker unit (which is 100W) and the newest Custer in Arlington, IN (which is 400W, and was installed about 6 or so years ago). As far as the speakers themselves go, we know that the Rushville and Knightstown units use the Atlas Soundolier Cobraflex style speakers. The controllers are simply fire truck sirens. Originally, the Rushville units were set on "wail" tone, but were switched to "hi-lo" as to not be confused with emergency vehicles. Each siren also includes a timer set to 2 minutes per-cycle as well as a Motorola radio. The sirens are DC only, as they use their battery and nothing else. Verlin says that the solar panels work very well and he can usually get 2-3 years out of the batteries before he needs to replace them. This way the sirens are completely off the grid, and there is no need to pay for a meter or even electric. It is also notable to mention that the only maintenance he has had to perform on Rushville's Custers is battery replacement. No driver replacements, no controller repairs, nothing- and this is after ~20 years of service. As far as sound ratings go, he measured the Rushville ones to be 110 @100', which seems reasonable. This was tested through having the siren on a ladder truck 100 feet away and measuring the output through a handheld meter. The main idea that he pushes is that the sirens are easy to maintenance if need-be. He uses all off the shelf, inexpensive items so that anyone could fix them.
Now for some information about specific installations:
As I said, Rushville's were installed about 20 years ago, making them 90's sirens. Knightstown's double-speaker unit was installed shortly after. Milroy was installed after that. Dunreith's was installed about 10-12 years ago, and then the one in Arlington, IN was installed about 6 years ago.
Verlin also works on other sirens, and here is some info on that:
He manages sirens for a good portion of Henry and part of Rush counties. He installed a Darley in Mays and a Model 2 in Raleigh. He also installed the P-15 in Lewisville. Something interesting about the Darley and P-15, he says that they both came from New Castle. This seems feasible, as New Castle's 2001-SRN's all have older yellow controls on them. The Darley was donated by a scrap yard after being removed from a water tower there.
Here are some photos of each different type:
Rushville 200W siren:

Knightstown 100W siren:

Dunreith 200W siren:

Milroy 200W siren:

And that's about it! It was definitely worth stopping in.