The serifs on the uppercase T in Garamond (including Adobe) are very distinctive. They point in the same direction, instead of being symmetrical as in Caslons.

Adobe Caslon’s W (uppercase) comes to one peak, while Garamond’s looks like two overlapping Vs

Adobe Garamond has serifs both at the top and the bottom of the uppercase C while Adobe Caslon only has a top serif. However, other Caslons, such as 540, have both serifs.

The center bar on the E and F in Caslon don’t stick out as far as in Garamond.

Uppercase P has a closed counter in Caslon
Uppercase G doesn’t have a nib in Caslon
Uppercase Q has a longer more flourished tail in Caslon
Uppercase S has different angles on the serifs (bottom is inward in Caslon)
Lowercase j has a ball terminal in Caslon
Tim

Got enough info to do that homework assignment now?

… you mean aside the fact that one is a baroque typeface and the other one a high-renaissance face and the 200 years of “refinement” in between? :)