1927 One Penny Error?

@will, first welcome to CCF. Second, I'm interested to see what our UK experts say, but when we see this sort of thing on US coins, we describe it as a "vise job", where a stack of coins is compressed and the designs partly transfer over.

Hello and

I agree that this is a 'vise job'. The penny has been placed between two other coins and pressed in a vice or struck with a hammer. On the obverse of your penny I can see the imprint of a George V florin of the 1911-26 period. You can see the design on the reverse of this 1919 florin:

On the reverse of your penny I can make out the letters 'IND' or possibly 'FD' and the vague outline of a portrait, but it's hard to tell which coin was pressed into it - maybe another George V penny.
Bronze pennies used to get treated pretty badly, especially by schoolboys with too much time on their hands - they had the combination of a large size and a low face value. I confess I once pressed a threepenny bit into a penny and then spent it, hoping that I might see my 'fake mistrike' featured in the next 'Coin Monthly' magazine - there was of course no internet in 1970!

Looks like damage to me.