Ok, I have had this coin for several years and am not sure of the date. This despite prooflike status that does not show up in the photos - it is the last digit that is tricky. What do you think? I know what I think (LOL)!
Have you checked the series for over dates? https://en.numista.com/catalogue/pieces13209.html Over dates check
It is a 1842 over 1.The die break(line) to the left of the date is present on other examples of this overdate coin. while your date is not as clear as others I think that is what you have.
Ah, JTL, very good. That is exactly right IMHO. I actually have the very rare 1843/54 groat as well, but it is really a pile! LOL. To the OP, well, in hand the coin is even more confusing as there are bits of relief metal to the right of the last digit as well as one below the putative top loop of the 2. But I do agree.