A photo has a unique 9-character identifier, consisting of 4 digits to express the date of the first work intended for the creation of a poster, generally the sketch, then 3 sequence digits, followed by a letter indicating the type of work:
- A: thumbnail
- B: sketch photo
- E: sketch
- F: painted photo
- M: mock-up
- Z: lithograph
Finally, a digit between 0 and 9 used when all other characters are identical.
