From Robert Bresson's 1951 film Diary of a Country Priest (Journal d'un curé de campagne). Here the unnamed protagonist, the priest of Ambricourt (played by Claude Laydu), holds a pocket notebook. He is often shown writing with a dip pen in a larger journal.
The film is available, beautifully restored, from the Criterion Collection:
Diary of a Country Priest
Moleskine datebook review
Moleskine sighting (In Ricky Gervais' Extras)
My other blog is a Moleskine