Can you post a photo of it to be sure it's a genuine Howarth and not an Italian import made for Howarth. Some of them made as recently as the '80s have four figure serial numbers beginning with 1. They won't have 'British Made' or 'Made in England' anywhere on them if they're Italian imports, just the Howarth logo stamped on the bell and the serial number on the back of the joints.
Genuine Howarth oboes from the '50s were usually handmade pro level models - the early S10 they were making from around that time is a conservatoire system oboe with nickel plated keywork with simple 8ve keys and no side G# key.