I restore these ~100 year old earphones so that they work with modern equipment. These earphones are most likely around 100 years old as the patents were filed in 1923. This restoration was on a pair of C. Brandes Inc. earphones. You can have a look at the original product catalog from 1916 here: https://www.sowp.org/wp-content/uploa... These sold for around the equivalent of $150USD in 2019 and all patents can be found under Dietrich Frederick. I was really excited to see if I could get these headphones working again. This was my first attempt at vintage electronics, so I tried to stay away from the more sensitive electrical components. Ideally I would have liked to have the coils all rewound, but the wires are 0.002" and that stresses me out. I need to work my way up to that. I decided to make only one modification and that was to remove the nickel-plating off the solid brass components. Nickel-plating was fancy back then, but now brass is fancy! Soap and water went a long way with cleaning up the headband. Sanding and polishing worked really well for the earphone covers. I was so glad I was able to hook these up to a modern headphone jack and listen to that sweet sweet sound of all metal speakers.