Coston's round included an eagle, seven birdies and just one bogey and is two strokes better than the previous course record shared by first-round leader Mike Small and Brad Westfall. Westfall shot a 66 in the 2002 Northern PGA Club Professional Championship.
Coston, a teaching professional in Blaine, Wash., had a 36-hole total of 10-under 134.
'I made a couple of long ones to start, and I told the guys I was playing with that maybe I should go into the parking lot and look for wallets,' he said.
Bob Sowards, the 2003 PGA Club Professional player of the year, was tied for second at 137 after a 68. Sowards is joined by Robert Thompson, who shot a 69.
Small, who cooled off with a 72, was alone in fourth at 138, followed by four other players at 139.
The top 25 finishers in the 72-hole medal-play tournament qualify to play in the PGA Championship Aug. 12-15 at Whistling Straits in Kohler, Wis.