This is the photo of the Eureka theater appearing on page 25 of Florin's book.  That's a 1960 Chevy wagon in the lower left, so this picture probably dates from about that time or a few years later.

Photo of a street scene in Eureka found on page 70 of Paher's 1993 book and showing the theater at right.  The other large structure, at left, is the courthouse.  This photo is undoubtedly not from 1993, though, given the automobiles shown.  Those would date the photo to the early to mid-1950s, most likely.

Here's the same building in November 2001.  It's now obviously an opera house, and the balcony has been substantially redone.