As I've mentioned here in the past, as part of my quest for player photos to make some of my custom college football cards I buy the annual Pigskin Preview issues of Playboy magazines from the 1960s and 1970s.
While I didn't find any player pix I have an immediate use for in the Sept., 1971, Playboy, I did find a lengthy article that might be of interest to today's collectors. The article dealt with collecting as an investment. The traditional "mature" collectible fields were covered: stamps, coins, furniture, art, silver, etc. While baseball cards were mentioned, it was exactly that, the two words "baseball cards."
What I found most interesting about the article was how timeless the advice was in terms of collecting with an eye towards future value appreciation. The article stands up well, even nearly 40 years later.
In an effort to share the article with collectors, I made a pdf and posted it on google docs. I've tried like heck to post a direct link to the article in my blog, but can't make it work. You can find the article by going to google docs and entering Playboy Collector article001.pdf in the search box., or you can paste this address into your browser:
It would be an interesting exercise to scour the article for specific mentions of various collectibles and their prices in 1971, and see how they've done since.