Common, not really, but in the big picture, probably more common than some of our short prints of the modern sets. The thing is, we have no idea how many actually exist, or that this happened to, etc. They are not catalogued here, but that doesn't mean there isn't a market for them. A player or a team collector will most likely pay quite a premium over a normally printed version of the same card. They are fun to find. I remember finding a bunch in packs back in 1985 opening Topps packs. I had a Gooden like that. I eventually sold it on ebay, but if I had sold it when I was doing card shows in the early 90s, I could've done a lot better with it. Oh well. I still have the 1985 Rod Carew in my HOF binder. :)
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).