The Siren Board

I'm looking for information about the Sterling M45. The fire department in Caledonia, NY used to have one as a backup to a Thunderbolt 1003. Both were replaced with an electronic Whelen in 2012 The Sterling was the town's original warning siren and was there before the Defense Department gave the town the Thunderbolt. It was actually mounted on a different building in the village before being mounted under the Thunderbolt on a separate siren tower. I have pictures of the siren and its data tag.

Fun fact: Caledonia is about a half-hour south of Rochester where Sterling made the sirens.

I tried to attach pictures but the site kept telling me the file is too big, yet no file size limit is listed? The siren looks like a M5 or M10 with a chopper/stator unit on either side of the motor. The only thing I can't tell from my pictures is whether it's dual-tone. Does anyone know if these were single-tone or dual-tone? I've only ever heard the thing twice in my lifetime and don't remember what exactly it sounded like.
Manufacturer's tag says:

STERLING SIREN
THE STERLING SIREN FIRE ALARM CO INC
ROCHESTER, N.Y.

MOT. NO. 575521
MOD M45
5 HP
NO 9158
3 PH.
60 CY.
VOLTS 220
AMP 18

Anyone know what year it was made?

I have some pictures I can post now:

This looks like a standard Sterling M5 to me, thought not sure what the M35 designation is all about. Not much to say about them really, other than the fact they were the most widely used horizontal siren here in the US and their legacy still lives on in Sentry Sirens. They came in low, high, and dual tone (8 and 16 ports)

Just checking in after awhile. Thanks for the response! That's too bad no one seems to know what the weird model number is about. If only my younger self got better pics of the stators! LOL