I have found 3 of the same type of objects as small as circuitry. I found them in my wall, connected to the iron fundament with a weird plug like holder. They were powered by a 0,020 volt AC power, which let me think it is possible working with telephony.
The item is probably made from iron and is gold-plated. I tried to upload an image, without it I cannot ask for identifying the object.
It is more likely there are no people who ever saw these like circuits. Still I want to try once.