ZUMBROTA, Minn. — What could be inside? A box, maybe 8-by-10 inches rectangular and a couple of inches deep, took a moment to give up its secrets. The time capsule, hidden away behind a cornerstone on July 7, 1961, in the newly constructed Bank of Zumbrota — later the Frandsen Bank & Trust — at the corner of West Third Street and West Avenue in Zumbrota, came to light two weeks ago when a Schumacher Construction demolition crew began tearing dow…