Thank you gents, I guess I had a feeling they might be mass-produced and quite recent, I just picked them up initially because I liked the shape. They are about 6cm high and 7cm across the gap.
When I try and upload pictures the site just seems to time out and return to the blank 'new thread' page. I guess my pictures are too big. I know there is a thread on here somewhere about posting pictures, I'll have to have a hunt!