To me, it appears that the two oblong marks have been disfigured with a graver, then over-struck with two other, perhaps meaningless, marks. If I am correct, these marks may have been applied by whoever cobbled the spoon in Victorian times, perhaps fearful and not fully knowing the details of the laws regarding the alteration of items post-hallmarking. I can think of no other reason why two likely official marks have been obliterated but the maker's mark left undisturbed.
If the marks have been destroyed, then it's all down to finding the mysterious 'WP' or 'WB'(?).