There's also a size that's smaller than the Medium. Don't know the dimensions but they have it in the US boutiques.
Here is a size comparison from the TODs website . Prices for calf leather.
Medium
$1595 USD
Dimensions: 13.4"W x 11.8"H x 6.3"D
Handle Drop: 3.9", Shoulder strap length: 37.4"
Large
$1665 USD
Dimensions: 15"W x 13"H x 5.9"D
Handle Drop: 5.1", Shoulder strap length: 37.4"
Travel
$1845 USD
Dimensions: 16.5"W x 15.7"H x 7.5"D
Handle Drop: 5.1", Shoulder strap length: 37.4"
Do you think they have the depth measurements swapped for the med & large? Can anyone verify that the med is about 1/2 inch thicker?