I'm a complete novice, only found this forum today, so apols if this question is naive.
I have two round-bottomed, flat-sided, wide-mouth jars (or, possibly, stoppers?) embosseed with regd No 784837. Which, I think, dates them to the 1930s. Industrial-looking not ornate.
They came out of dredgings from a canal in Shropshire 30 years ago, close to a former fertiliser factory.
They have threaded openings for a lid but are round bottomed and flat-sided, so can't stand up unless upside-down. It is, perhaps, possible they are actually some sort of stopper for a larger vessel. But as the openings are about 4 inches across it would have to be a very much bigger vessel.
Any clues or thoughts welcome, thanks.

There is an image on imgur at
https://imgur.com/aAo6301