KY,
Your questions cover about the whole gambet of change in the 300 series.
Basically look at it this way, early on Buck contracted 300 slipjoint construction. Contractors used industry standards of the time which was brass liners and flat blade grinds, during the eighties Buck decided to do it themselves, they used the old format with a couple of modifications to get started but then came up with a whole new way to make them in the 90's which kept going and going. Some changes have occurred to those also such as grinding changes, finishing changes and scale material change
Flatground blades were the norm till the 90's when the bevel edge design became popular over most of industry. Same thing happened with brass liners, they were around in 300s till Buck went to all stainless construction. Notice also they went from 2 springs to three. One for each blade, saves dealing with the offsetting of the secondary blades. (krinking - mainly a hand operation)
Notice now that all 300 versions are all stainless. In the sawcut version the famous knife,bolt and hammer escutcheon plate is actually a solid hunk of metal that is intergal to the liner. Goes up thru a hole in the 'thermoplastic' sawcut scale. Same with the Blue Anvil shield and Dymondwood.
Changes get made sometimes to make a better knife and sometimes to ease manufactoring costs and methods without changing the precieved quality of the knife. But that could be marketing opinion.
Brass is expensive, soft and tarnishes, stainless is cheaper,harder and well, stainless.
No BS now. The Buck slipjoints made today will outlast, outwear and sharpened correctly, likely outcut the Bucks of the past. We all have a tendency to favor what we grew up with and what the people who were important in our lives favored. I still like to polish brass, I still like jigged bone. I guess someday I will be saying the same thing about nicklesilver and Delrin.
300Bucks (Sorry KY I may have rambled here, tell if I confused you)
PS: Knarfeng explained the grind per-xactly..