From what I've experienced / learned, there's been a progression of odd & ends improvements over the years in their locks in general because with the exception of a couple unique parts, a lot of the parts are identical in both the percussion and flint lock assemblies...but the most significant changes to the flint locks themselves seem to be with the frizzen and hammer.
The frizzens are harder for better sparking and longer life (old style is case colored, newer style is solid black);
The improved hammers are taller and have a different "S" shape, striking the frizzen at least 3/4 of the way up, and with a better 'angle-of-attack' on the frizzen.
The older style locks had a reputation for eating flints because they struck the frizzen face too straight on (too square) and way too low so they didn't have much leverage to tip the frizzen back easily and met a lot of resistance which also contributed to flint breakage.
As I mentioned, using 3/4" black english flints, the newer design locks give plenty of sparks and 40-60 shots per flint.
I've been shooting them going on 3 years now and I don't know what else a lock could do...they're 100% reliable and I'm not generalizing when I say that...I don't mean they're approximately 100% reliable, I mean they're 100% reliable. You don't have to tinker with them, or 'work on them', or modify them, or hope and pray over them...unless you have wet powder or a dull flint, when you drop the hammer the lock will fire the rifle right now.
As an aside, TC also introduced a significantly improved, redesigned vent liner which is extremely fast...ignition is just a single instantaneous event...I've shot them at the range almost every Saturday year round and it's like shooting a .30-30.