I found this today. The description states that an air raid siren was used instead of a bell, but I cannot tell exactly what the siren is. Perhaps a pair of Model L's?
The description from the site is as follows: "Siren Crossing Picture of the famous Siren or Screaming crossing as the locals around here used to call it. This device had neon lights and an air-raid siren that could be heard all over Grenada. This device was developed by W.A. Billups, a Grenada native. This crossing had numerous deadly accidents, one of which was someone in his family and thus inspired him to create this unique warning device. Mr.Billups tried to market his invention but the idea never took off and to my knowledge, this was the only one ever built. The device was installed in 1940 and lasted until 1970. The crossing is still here but all that remains of this device is the concrete blocks that supported it. Picture was taken sometime in 1940."