As far as letter J’s go, this one might look a bit more like it could be something else. But, this pretty letter J engraving is indeed meant to be the 10th letter of the alphabet.
It was included in a 2-volume French work from 1867 which featured fashionable ladies as flowers. The drawings are more satirical than the sweet little girls and their flowers from A Flower Book but the letters the printer used are wonderful.
There were 13 letters included in the 2 volumes and you can find all of them here – French Printer’s Letters.
The pretty letter J engraving features a letter that is decorated with circles and crosses. Climbing up the J is a grape vine with several bunches of grapes.
This image is copyright free and in the public domain anywhere that extends copyrights 70 years after death or at least 120 years after publication when the original illustrator is unknown.