That looks like the 1981 Away kit. Number 11 is Stuart Lee who played for the Bolton Wanderers, Wrexham, Stockport County, and Manchester City before coming to the timbers for 2 seasons. He later played for a slew of NASL teams including the Kansas City Comets, Carolina Lightnin, Los Angeles Lazers, St. Louis Steamers, Tampa Bay Rowdies, and Dallas Sidekicks. Number 21 is Jimmy Kelly who hailed from Northern Ireland. He had 2 stints with the Timbers and also played for Glentoran, Cliftonville, Wolverhampton Wanderers, Wrexham, Walsall, and the Kidderminster Harriers. Wish I could tell you more about the source of this photo, but that’s the internet for you.
UPDATE: Found the original online source, of course it is NASLJerseys.com. Still no idea what the original print source was. Obviously some Timbers advertising. This page also identifies the other players in the picture. Bernie Fagan (18), John Bain, Bruce Gant, Kenny Palmer (dressed as ref), Willie Anderson (12)