HI Guys
I am too excited to wait until I get home and get proper pictures and weight.
I recall somebody posting a different coin in the past with this error, but I cannot find it. I think it is a struck through a capped die. The theory here is that this is struck through a coin that was stuck in the collar after the strike. The obverse is normal, the reverse is a incused impression of the obverse. The coin appear to be a UK farthing 1949-1952 based on design and size.
It is of course possible that this is a "made" error.
Please let me know what you all think. Worthy to note that the initials beneath the bust are not present.

