The auction call this a team issues postcard. It's a nice card. But I don't know about it being a postcard. The back is blank. So it could be a reproduction but at least I know the picture was taken in 1976. I did a search for other Oriole postcards and found a Brooks Robinson Triute page that had a similar looking postcard so I'm fairly certain its authentic. It measures 3 1/2 x 5 1/4 inches.
I got most of my facts from http://www.thebaseballpage.com/ and wikipedia.
Oh here's an interesting tid bit I didn't know, even being a Milwaukee Brewers fan. The Baltimore Orioles can trace there heritage back to the original Milwaukee Brewers baseball club from 1901. And now you know.
Happy New Year everybody.