Smile on my face

Its a 'delay bevice'. Basicly there's a speaker on one end of the spring and a microphone on the other.
Sound comes out of the speaker, travels thru the spring and goes into the microphone.
The time it takes to travel the spring is the 'delay period'.

They used to be very sought after by guitarists looking for a delay setup for their amp/speakers.



This is a more modern one from a TV,
The signal travels thru the glass this time.

I cannot find a image of a SMD device, they are easy to find, the stainless steel rectanglar box on circuit boards.
Grind the top edges to remove the cap and inside is a beautiful crystal etched with lines on it.