Found another one in a box! This one is 34cm (13.5") diameter, and weighs 685g. Very hard to capture the colour.....it's very pale pink. 16 ribs to the base, wide Wrythen rim. It has a proper folded over edge that is not completely flat in some places (see picture).
Unfortunately, water/debris has built up under this folded edge - any ideas how I can clean it, as I can't get anything into the gap?
When we were discussing these pieces, I was so focused on the number of ribs that I didn't consider that there are distinct differences in the finishes on the edges. The ruby piece has more of a moulded ridge to the rim, the edge on this one is actually folded over, and John's gold one appears more of a flat, unfolded rim.
I will get on and contact the museum about these pieces in the next few weeks.