According to Andrew Sandoval's The Monkees: The Day-by-Day Story of the 60s TV Pop Sensation, "Daydream Believer" b/w "Goin' Down" - the Monkees' fifth single (Colgems 1012) - was released in the U.S. fifty years ago this month (November 1967). The U.K. release (RCA 1645) was released the same month.
The catalogue number that Sandoval lists for the U.K. release is the same as what he has for the "Pleasant Valley Sunday" b/w "Words" single. I'm not sure if that's a mistake or not, or - if it is - which number is erroneous.