Night Owl. If you follow Mr. Owl's blog at all (and why wouldn't you?), you should have known that an older mystery card from him could mean only one thing...
Did I get that right, Night Owl?
Yes, my fellow card blogger and vintage enthusiast is closing in on completion of the 1975 Topps 2 1/4" X 3 1/8" parallel set just as I whittle my base set needs down to the nitty-gritty. He actually sent me a pair of perfectly imperfect copies of Dave McNally's mini card. In addition to the lovingly creased card you see here, there was another that was stupendously miscut on the top and bottom borders. They will be added to my team collection with nary a discouraging word. Though I seem to have successfully acquired all of the Orioles' Topps base set cards from 1973 through 1978, I haven't really gotten moving on the 1975 Minis. In addition to this here McNally, I've got Grant Jackson and Jim Palmer...at least I think I have Palmer. Note to self: you've still got a lot of organizing to do.
Anyhow, for the sake of comparison, here's a scan of Dave's 1975 Mini alongside the full-sized card. It really is slightly smaller! Wonders never cease.