What is it?

Can anyone help me identify the round metal thing in the lower left hand corner of the picture? I can't reference it in my service manual until I know what it's called. Is it supposed to be there or is it an aftermarket part? The only set of wires going to it (that I can see) come from an aftermarket car alarm I am attempting to remove. I haven't seen it in any of the other pictures of 450SL engines I've run across.

Thanks
'76 450SL

[kip Foss]

It looks like a very old style bell which could be connected to an alarm system.

[den500sl]

...might very well be the car's horn?

Forecast of 55F for Chicago tomorrow and a day out for the SL. Yippeee!

97 sl500 triple black
sport pkg1
24k miles