So much blue...
My own baseball collection kicked off in early 1980 and as a recent transplant to Washington state, Tom "Wimpy" Paciorek's card stood out. (Love that white-blue helmet and double batting gloves!) After three years of the expansion-era "Trident M," Seattle's logo evolved to this angular, star-shaped background in 1980.
Only a few months into my pack habit, the growing stack of cards got an unexpected bump back with a 1974 Hal Lanier. Wow, I remember thinking, that's a seriously old card. This is what real collectors own, and now it's mine. (Also compare those "banner flag" 1974 and 1980 set designs, where one obviously cribbed from the other.)
Nice auto! (Sadly, not my card)
Sometime in 1981, a garage sale turned up this 1971 Kellogg's Jim Palmer. It was only one of many in a 25-cent plastic bag, but stood out as both a great player and older than I was.
Good photo, weird background
Things got murky over the next decade as I moved in and out of regular collecting, but this card represented my move into the sport's golden age. That early 50s hand-painted look is still fabulous and cost $2 on eBay, circa 1999.
1952 Bowman #73 Jerry Coleman
Once the #5 blog kicked into gear, all kinds of oddball cards found their way into my collection. Most of the oldest sets went unnumbered, so won't end up there, but a couple of 19th-century (!) issues qualify. The oldest now--and likely to stay that way--is an 1886 tobacco issue featuring women posed as baseball players. (A close look at this slightly blurry scan reveals a prop string holding the ball in place.)
1886 Sub Rosa Cigarettes #5
Move back any further from 1886 and you're looking at seriously rare and expensive stuff. (I consider it a minor miracle this #5 ever turned up, let alone proved affordable.) Should it remain my collection's oldest card, you won't hear any complaints.
Thanks for the posts, Greg and Chris, I enjoyed filling out the concept!