Saw a new 10 ounce coin on the Provident Metals web site today.
10 pound coin
89.15 mm is the diameter
weight 311.52 g
This is the first coin by the royal mint to feature a incuse design; This coupled with the beautifully detailed frosted finish make this a brilliantly eye-catching coin
They are saying that the background is a guilloche design. So I looked that up and got the following definition - ornamentation resembling braided or interlaced ribbons.