British Penny Question

A friend has an 1877 British Penny . How can you tell if its a large date or small date ? I see that the small date is worth a lot more.
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A friend has an 1877 British Penny . How can you tell if its a large date or small date ? I see that the small date is worth a lot more.
Comments
Here is a good example showing the biggest difference
Small or narrow date is top one.

Thank you, very much appreciated.