Before the establishment of Sekine Canada Ltd in 1973, the bicycles had to be imported to North America. Beacon Cycle was perhaps the only (confirmation, anyone?) Sekine distributor in the United States.
These made-in-Japan Sekines are readily identified by the "World Finest Bicycle Made By Sekine" decal on the down tube, also sporting a Jewel head badge, and are Suntour equipped. I've seen and read about a few of the bikes found in the United States that have a Beacon Cycle decal somewhere on the frame, and I've also seen what appears to be a factory "Distributed by Beacon" Sekine decal on the seat tube. May look something like the one pictured*
I was pleased to find more information about Beacon on Howie Cohen's Everything Bicycles Collection. It seems Beacon had strong ties to Japan, which probably lead to the relationship with Sekine.
It seems that after the establishment of the Canadian factory in 1973, North American distribution was controlled by the Acklands Co. of Winnipeg. It's not clear yet if the relationship with Beacon Cycles was continued, and there's evidence Sekine was attempting to expand their U.S. dealer network.
*Photo linked from Hdacy's Sekine Flickr set