An old chestnut ??

I found this thing today and when MightyMouse asked me what it was, I was a bit unsure ... I'm assuming it's an old chestnut??

Have you ever pondered over that expression 'an old chestnut', which according to a dictionary means "a joke or subject that's been discussed or repeated so often, it's not funny anymore"?

Another strange expression in the English language.

Maybe it's not even an old chestnut. I might have a look inside tomorrow.