Hello, “snap” I think. Some dessert spoons that seem to be marked like the serving spoon that was formally imaged in this post. My spoons have the "IR in oval cartouche" belonging to John Robertson I, with a pellet between the letters. I assume the missing image also had the pellet present.
The date letter is “G” and that was used for 1797 and we can see a cusped / indented "duty mark". We now know this was a “limited use” mark that indicated a silver duty rate change. The duty had changed in July 1797. and prior to the use of this cusped mark, 2 standard duty heads had been struck on items to indicate the change. An example taken from another post is below.
Apart from sporadic findings (I’ve seen 1), the cusped mark ceased to be used part way through 1799 when the duty mark showed the Monarch's head with a concave "bust base". This image does show the Newcastle Guild mark with the 3 castles that has been left "unstamped" on my spoons.
There is more about this Newcastle duty head changing period in the post referenced below
https://www.925-1000.com/forum/viewtopic.php?t=13577.
Fishless