Hello!

I need help trying to find the title of a movie british? In the 60's? Or 70's?
Synopsis: A group of children in search of a treasure hidden near an old water mill. By opening the trunk, we realized that it did not contain a true treasure, but chocolate coins!

This is not Treasure at the Mill (1957) by Max Anderson

Can anyone tell me what movie this is?
Thank you for your help!

Did you see it? What did you think of it? We think this is the series TV!

"The Barnstormers" Mystery at the Mill (TV Episode 1964) - IMDb