Hi Leonie,
The bmp isn't too bad, I will have a go at it but hopefully someone else who's better at cleanups will also attempt it.

Unfortunately, tintypes lack alot of tonal information so it will be difficult to get much out of the black and highlight areas in your pic, but at least it might come out looking a bit neater.
I live in Canberra so I might pop round and take the hammer off your rellie!

Prue