I had forgotten about this post. I've recently been looking into hallmarking on Newcastle teaspoons, and this lion jumps out at me now in a way which it did not two years ago. As you know, Trev, I've been looking for a Newcastle incuse duty mark, so perhaps my eagerness might be clouding my judgement.
The lion resembles very closely the lions used on many confirmed Newcastle spoons at this time. Compare it to the Langlands and Robertson spoons. I know Jackson's and other hallmark books put the Newcastle duty in a roundish cartouche, but, as we both know, teaspoon marking has a law of its own. See the duty mark on the Pinkney and Scott tongs.