Spot the Difference

Can you see a difference between these two Club biscuits?

When my dad retired he left a little joke behind in an office drawer.

The chap who was tidying out his room opened the drawer and was chuffed to bits to discover about 50 Club bicsuits, of all flavours. Until, that is, he picked one up. It was too light to contain a biscuit. It was, in fact, only the wrapper made up to look as if the biscuit was still there.

It was the same story for every last one of the apparent biscuits, which was a great disappointment to the fellow. After learning this trick from my father, I find it hard to eat a Club biscuit without feeling the need to re-wrap it and make it look like an uneaten biscuit.

Only one of the Clubs in the picture actually contains a biscuit, the other is an empty wrapper, but which is which?