1/3 Farthing 1844 Overstruck On. ?

Ciao,
have you ever seen a similar overstrike on a fractional farthing?
The signs of a previous strike are very clear and they are in relief in the area of the neck, disappearing gradually where the reliefs become higher, then is definitely not the case of a countermark.
In fact, the signs look as numbers struck in negative but in relief (1, 7 and maybe a part of an horizontal 3?) and punched sometimes one over another. For example another upper part of the sign similar to the 1 is visible onto the sign similar to an horizontal 3, on its right. And also the reliefs of the other signs show other previous strikes here and there.
This make me thinking that the first strike (or strikes?) could be not a normal coin but something else.
And here is the mistery. what? Ideas are welcome!

Have a good day,
Roberto