I have a customer's '51 Ford sedan in the shop today that has an aftermarket disc brake kit on it - unfortunately neither the owner or I can get any information on this car as it was bought from a consignment site that hasn't been particularly responsive to our attempts to reach the builder. I pulled the front wheels because it seemed to have a little leak in the wheel seal and found the inner seal had a big ding in it but there's no numbers anywhere on the seal and I don't know what rotor this is so I wondered if anybody here might recognize the brake setup and know what seal it uses. The rotor has 5 notches in it between the studs (5 on 4 1/2") that I thought might be a way to ID them - the seal seems to be 2.5" OD and 1.688" ID and has a sort of rounded lip at the top.
Dig your caliper out, measure the spindle then measure the inside of the hub where the seal fits. = ID & OD then go to a seal chart and figure it out. Napa says that the stock 51 seal has and ID of 1.688 https://www.napaonline.com/en/p/NOS16743 The front wheel seal for a 1990 Ford Aerostar has an OD of 2.504 https://www.napaonline.com/en/p/NOS19214
The Shoebox Central guys sent me an e-mail saying the seals are SKF 16871 - NAPA number is the same. It's actually a trans seal.