It is the 708, but it is not a butter. It is a honey pot. The lid has a slot on it. I have three different honey pots, and photos of several more. All are British, all have an attached underplate, and all have a domed lid with a slot in it. I also have some catalog illustrations that show the word 'honey' under the dish. (I have a complete one of this #708)
Here is a picture of a catalog illustration from Percival Vickers, and the honey pot that matches it. (still looking for the one on the left side).
The other photo is a small copy of an article I did on English honey pots a couple of years ago.