What is a tuppin?

Answer 1

I presume you mean a "Tuppence" or Twopence.

It is a British coin, very rarely minted in the past 200 years, but a bit more common earlier on, that was equal to two Pennies, ie. Twopence or Tuppence or in earlier days again, a Half Groat, a Groat being Fourpence.

Answer 2

The word is tuppence, not tuppin. It is a coin from the United Kingdom that is valued at two cents.