Also see this older thread: Crosby Lane Fox Crosby Lane Fox 342 $950 sizes 20 & 21' -- flat seat with round cantle. Was $950 in whatever Miller's catalog I looked in, probably a 1994-1996. Standard safety stirrup bars. Crosby Lane Fox 300 & 302 -- 19, 20, 21, and maybe 22' -- flat to almost mid-deep seat with square cantle and standard safety stirrup bars. The 300 has a more dished / deeper (mid-deep?) seat than the 302, and might be the earlier model.
The 302 is very flat. Crosby Lane Fox 303 -- 19, 20, 21 -- Deeper equitation seat w/ higher round cantle Crosby 303AB is the deep equitation seat with adjustable stirrup bars. 19, 20, & 21'.
I've never seen a deep seat 22'. Crosby 302AB flat seat square cantle with adjustable bars apparently does exist but must have been by special order only. I saw one on eBay but not in any Miller's catalog. All of the Crosbys were made in England on the Plybond tree.