How do you know the PRs for Letter cards?

[56Parkies]

Draft Day Marks are /35 for each letter (or /10 for each for the star players, as mentioned)

Panini Namesakes are 75 total copies, so varying print runs for each letter (those print runs are not released). Same goes for other sets over the years, such as the SPGU Letter Marks, Team Marks, (50 copies total) etc. as well as the 08-09 and 09-10 UD Black Rookies (399 total IIRC)

Tell me about it! I'm STILL trying to track down an S for my Osgood collection.....