Thank you for your response. I did consider Daniel Beets, but the “D” on this spoon is very distinctive and does not match any examples of his punch which I have seen. He was also working rather later than the style of spoon would suggest. Although style in colonial silver cannot really be dated along the lines of English fashion.
The punch is definitely worn, as can be seen by the distortion recurring at the top of the initials on both strikes. It is possible therefor that the examples in Stephan Welz’s book are of later replacement punches.
The joint on the back of the spoon is a simple union joint, so no real clues there. I have looked at all manner of colonial silver; Cape, Australian, Indian, Canadian etc, also British and Irish provincial, but have not yet found an exact match. I might just have to put it in the “unsolved mysteries” file until something materialises.