on cassidy's, referring to the bottom left most symbol as 1,1;
1,4 (top left) seems to be a 7 or a Z rotated around; 2,3 looks like a 6 or 9 on its side and rotated; and 2,1 is a 2 rotated
4,3 looks kinda like an 8; 1,2 might be a 3 flipped; 3,2 might be a five flipped.
none of the others are interpretable and I don't see an overall pattern to it.