What is a closed 3 and an open 3 on a 1903 British Penny?

Answer 1

A normal or closed "3" has the curves continuing in an arc to the left. An "open 3" would look a little more like an "8" that had been cut in half vertically.

The related link below shows a "closed 3" 1903 British Penny.

Answer 2

The peculiarity with the 1903 Penny is the "3" in the year.

Some coins have a normal "3" where the ends curl around to almost form an "8", ie, a closed 3.

Others have a "3" that looks as if it might be an "8" cut vertically from top to bottom, ie. an open 3.