Here are some photos of the first stove I ever owned. It was bought new in 1960 and we used it on a long family car camping holiday, starting in Sussex and ending up a few weeks later in the Northernmost part of Scotland. We stayed with relatives for a week or so, then came South again, camping all the way. My father died in Dec 1962 at the age of 44, so the memories have been important for me and the dates firm. This stove, is an Optimus No 45S, it turns out, and has a sunken filler and an air release on top of the filler cap. The illustration in the 1957/8 Optimus Catalogue introduces the "new" Op.45S and 48S, featuring the new, for Optimus, sunken filler tube to ensure the tank cannot be over-filled. https://classiccampstoves.com/threads/1957-58-appr-optimus-catalogue.9292/ However the catalogue illustration shows the Op.45 and 48 with side mounted air-releases on the neck of the filler. But who trusts illustrations in manufacturers catalogues and box illustrations? Yes, I know the flame ring is marked Primus, Sweden. It is a later addition. Best Regards, Kerophile.