Palmer retired in 1984 with 268 wins, 3 Cy Young awards, and 3 World Series rings, all excellent support pillars for HOF election in his first year of eligibility. Many considered him a shoo-in for Cooperstown by the late 1970s, both for his personal fame ("underwear model" will do that) and as a key piece of Baltimore's great success in the 1960s and 70s.
Walker's announcement took me back because Jim also un-retired in 1991--a year after reaching the HOF--and joined Baltimore for spring training. Jim's comeback only lasted two innings of a single game, however, before he hung 'em back up--and that's in a non-contact sport. There's no questioning Herschel's toughness (MMA at 48!), but expect the same story to play out should he try a gridiron return.
Kellogg's settled into their sorta-3D niche by the late 1970s and this 60-player set repeats what worked for them throughout the decade. According to the Key Man Collectibles 1979 profile, three print runs spawned a bunch of variations, so the master set contains over 100 cards.
Value: Most Kellogg's cards cost a dollar or two and even less if they have any surface cracks. Find Palmer and plenty of others at Check Out My Cards.
Fakes / reprints: Haven't seen any Kellogg's fakes in the marketplace.