As Paul says, they can be old. Iran and places in the East are still making the same patterns as several centuries ago, and difficult to date. This business can supply you with old or modern locks — they have grown quite knowledgeable about padlocks:
https://scaramangashop.co.uk/collections/antique-padlocks
There are medieval screwkey padlocks from Europe, but they are not common and might be pricey.
However, the Abraham Thompson screwkey lock is a safe choice. The early ones have a small brass diamond mark, usually poorly stamped. It’s one of the few locks protected by design registration, there being nothing novel about it which could be patented. There were three sizes; the smallest is rare.
" This firm was established in 1831 for the manufacture of all kinds of padlocks and night latches for home and export. Thompson seems to have sold most of his locks to the United States, as a number appear for sale there. From 1851 to 1861 they were located at 28 Temple Bar, Willenhall.
They remained there until 1912 when they merged with Jonah Banks & Sons, padlock manufacturers, of Clothier Street, Willenhall. Banks went into receivership on 5th January 1993 and their factory closed shortly after."
From 1912 there is no diamond mark. It’s not clear when Banks ended production of this design, but the same design was sold by Benjamin Walters through to 1939. Walters locks are stamped with the Staffordshire knot.
Note that Hiatt darby handcuff keys will not fit these padlocks. Hiatts also made a brass barrel screwkey padlock, but I’m not sure if there are any old enough to be antique. The pattern continued in production until the late 1960s, called ‘dutch padlocks’.
