The 1953 incident was captured on a stamp issued as part of a set a few years ago – that was why the Queen's head featured in the scene, of course.
And now former postman David Evans of Shrewsbury is trying to solve a minor mystery. Who is one of those two men featured in the stamp?
The occasion was probably less dramatic than it sounds, harking back to days when the railway line actually ran along streets in Welshpool centre, and no doubt the car was simply being moved to make space for the steaming loco called The Earl to pass.
Dave said: "I was a postman for over 38 years and took an interest in the stamps I saw on letters, and collected first day covers for a number of years.
"For 12 years of my Post Office service I spent in Welshpool and for some reason I decided to make inquiries of a local stamp with the Welshpool & Llanfair Light Railway locomotive, The Earl.
"A local garage owner told me that the one person on the stamp was Alan Ballard who sadly passed away two years ago. I wonder who the other person is facing the train while moving a motor car from off the railway line in Union Street, Welshpool.
"I have some recollection of this man and certainly remember Alan who is dressed in a boiler suit turning away.
"I then noticed that the stamps were issued in February 2014 with a postmark of Porthmadog. The choice of trains was quite a surprise, especially The Earl, because it was not of huge importance, but I was pleased that it was featured in the set of stamps for Wales. This image was taken in 1953."
The others in the four stamp set issued in 2014 on the theme of Classic Locomotives of Wales were Hunslet No 589 Blanche passing Pen Cob halt on the Ffestiniog Railway in 1964; LMS No 7720, a coal tank leaving Britannia Bridge in about 1930; and BR 5600 No 5652 heading a coal train at Cwmbargoed in Merthyr Tydfil in 1959.
"I was not sure why BR5600 No 5652 was included, just chugging along some empty moorland at Cwmbargoed, Merthyr Tydfil. Then I learned that that was where Cornishman Richard Trevithick had run the world's first train to be hauled by locomotive.
"Blache on the Cob on the Ffestiniog Railway is in some ways my favourite. Y Cymro, or The Welshman, steams away and seems the emblem of all the trains of Wales."
If you can identify the man in the stamp picture, or know of details of the incident, do drop a line to email@example.com