i took this doorbell off my house because it was abandoned and a different doorbell was put in. my house was built in 1880 and was wondering if this could be the original doorbell or possibly earlier or later. when trying to unscrew it, i scratched some patina and it looks like brass. the screws look hand forged because the groove is not in the exact center of the screw. there is another doorbell exactly like this but square shaped on the other door to my house and may take that one off as well. any idea of the age or value of a doorbell like this? thanks