Indent strikes are very common in the early 1960s through to 1981... but you almost never see them on older coins.
This was a coin I acquired as part of the same lot as the other George VI errors I recently posted. Again, like the others, I suspect an old cleaning had occurred with this coin. But it is a keeper for sure. This is the only George VI 1-cent I have seen, with an indent strike.
"Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert Oppenheimer