I bought another pair from the place I got my other ones. They go *pop* when power is applied as any out-of-tuning horn would on 6 volts. The main issue is that these horns have no form of identification on them at all, inside or out. Maybe the horn fins and diaphragm housing design will be enough for a horn-savvy person to figure it out. Like the last set, I paid $20 for them.
Can a horn-savvy person help me figure out who these were made by, the proper voltage (6 volts doesn't sound like the right voltage), and the year of production?
Pictures: https://www.flickr.com/photos/123117836@N06/