Cathy - this is not an easy piece to photograph - somehow the light seems to bounce off a little too much, and trying to capture the surface pitting/corrosion is difficult. However, this evening I will have another go and post some more pictures for you. On the first Tuesday of the month (afternoons only) the V. & A. in London offer a 'you bring it in, and we just might be able to tell you what it is' day, so I will take this piece with me. In view of Christine's offering taken from the museum's technical notes, I'm hoping they are able to be more positive on this particular piece. As far as I know, the appearance of 'Sea glass' is due solely to the effects of abrasion by sand and pebble, over a long period of time - a giant sized tumbler in effect.