Because it shows the gas lamp which stood for years at the centre of the bridge arch and presumably gave welcome illumination for people and vehicles crossing the structure over the River Severn.
The photo comes from Paul France of Madeley who has received a couple of parcels containing various photos and books from Liz Wheeldon, the widow of an old pal of Paul's, Jeff Wheeldon.
Jeff lived and worked in Ironbridge in the 1960s and 1970s before moving to Seaton in Devon.
Among the material to come Paul's way is a postcard franked in June 1904 showing the lamp in situ at that date. It was not an original feature of the bridge and had perhaps been installed a few years beforehand.
In an effort to find out more about it, Paul put the picture on a Facebook page, called "Ironbridge through the Dale Yesteryear," and says there were plenty of responses.
"The general consensus is that it was a gas lamp with a metal cover to the pipe and a small metal box about a foot high that kids used to stand on," he says.
Very few people will still be around who can remember it, as Paul says it seems to have disappeared in the 1940s.
The Iron Bridge, the world's first significant bridge made of iron, was built by Abraham Darby III in 1779.