There are a number of patterns that Case labels as "Medium Stockman":
'344 - 3 1/4" Small humpback style, squarish bolsters
'3087 - 3 3/8" Round bolster serpentine (same frame as the Pen and Medium Jack)
'3090 - 3 3/8" Round bolster equal end, stubby cigar.
'318 - 3 5/8" Round bolster serpentine
'318PU - 3 5/8" Round bolster serpentine with punch
'3032 - 3 5/8" Square bolster serpentine
'3046 - 3 5/8" Humpback
'347 - 3 7/8" Round bolster serpentine
Of those models I only own a few (63090, 63032, 6347) and the one that gets the pocket time is the 63032, Chestnut Brown CV model. I don't have any experience carrying or using the '18 model.
I really like the 63032's profile and blade combo. Other than the bolster shape, the only difference is the 3rd blade is a pen rather than a spey. On the 3318 it's a spey or punch.