I ran across this super cool cardboard display sheet, advertised as being from the 1950s, in an older auction catalog from December 2000. I've found a few more examples online, but with no additional historical info.
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Hobby News Rooted in History
I ran across this "very striking" 1950s Ted Williams Moxie die-cut advertising sign in an auction catalog from December 2000. 
Here's the original flexichrome artwork for John Huarte's 1965 Topps #117 Football card.
Here's one of the scarcest non-sport collectibles in the hobby from the Walter Johnson Candy Company, a 1930s Dick Tracy R41 set wrapper. 
T.S. O'Connell wrote an excellent article for Sports Cards Magazines' April 1995 issue about World Series Cards; these were his Top 10. What do you think about the list?
In 2005, Sotheby's offered a collection of some of the scarcest Pacific Coast League cards in their Important Sports Memorabilia and Cards auction. The lot included 136 cards, plus a few original mailing envelopes, of the four Centennial Flour's Seattle Rainiers sets issued between 1943 and 1947.
If you got a grand or two, here's a fun one to add to a baseball card man cave: Lou Gehrig's Official "Plaball" Baseball Game.
You know what's cool? A plastic radio with facsimile signatures of Roger Maris and Mickey Mantle!
When Babe Ruth and Lou Gehrig appear in the same ad, you know it's a legendary piece of baseball memorabilia. 
Yesterday, I shared an ad from The Baseball Card Kid, with whom most collectors on the leading unopened FB group had fond memories. This ad from Prince of Cards didn't precisely elicit identical memories.
Today, the Baseball Card Exchange is the big player in the unopened space, but in the early '90s, it was Mark Murphy, The Baseball Card "Kid." Here's an ad he placed in the December 1993 issue of Sports Cards Magazine. 
I ran across a rare item in Ron Oser Enterprises' April 2001 catalog described as a 1966 Exhibit card uncut sheet from the last year that exhibit cards were issued. But I don't know that the description was accurate!
More on the blog:
A Rare 1966 Exhibit Baseball Uncut Sheet? – Post War Cards
I've previously shared the original artwork for the 1953 Topps Willie Mays and Whitey Ford cards that Guernsey's sold in its famous 1989 Topps Auction. But other examples have also tricked out over the years, including this one of Ken Heintzelman.
I ran across this window sign advertising the circa 1937 R342 Goudy Thum-Movies in Sotheby's March 1991 auction catalog, which included The Copeland Collection; it's a cool-looking sign in black and white, but it's actually red, white, and blue.
Here's one you don't see every day, especially in triplicate: a 1984 Topps Football Cut Card Case! One of each sheet (“A”, “B”, and “C”).
Reggie Jackson is known as a first-ballot Hall of Famer, but did you know he also had a passion for classic cars? In the early 80s, Argus Publishing released a unique set of three cards featuring Jackson alongside some of the vehicles from his personal collection.
The 1980-81 Argus Publishing Reggie Jackson Cards – Post War Cards
Here's the original artwork Dick Perez painted for the 1984 Donruss Mike Schmidt Diamond Kings card.
What's super cool about the 1955 Topps Doubleheaders uncut panels is how clearly they show the continuous artwork designed into the backgrounds on the cards! 
Who remembers when super premium packs were just $5.99? Anyway, the Dec 1996 issue of Sports Card Trader had an excellent article about Mike Cramer taking on the goliaths of the industry that I wanted to share.
Pacific Takes On The Goliaths – Post War Cards
Who doesn't love the mouse? These four sheets from Gum Inc. were auctioned off together in April 2004 and included three from the R89 Mickey Mouse set, and one from the R90 Mickey Mouse with the Movie Stars set. 