The model is Sports Tour, based on the top tube decal. I'd place it mid-1970s. That version of the SunTour VGT rear derailleur was manufactured circa 1974-1977. I can't positively identify the crankset from the non-drive side photo but it appears to be a Super Maxy, which was introduced in the mid-1970s. I'm pretty sure the Power Shifters weren't available until the 1970s. Regardless, both the rear derailleur and crankarms will have manufacturing date codes stamped on the back. The frame serial number should also allow us to determine the year. Picture assist...