Sannow was the house brand of a bike wholesaler located in Tokyo, most active around 1960-1980 from what I’ve been able to learn. No two Sannow frames you can find online are alike (were they custom? I don’t know). This frame is likely from the mid 1970’s and made of Tange #2 tubing. 57cm seattube, 57 cm toptube. Currently built with a mix of top-tier parts appropriate to a bike being ridden in the early 80’s, but with modern consumables and Dura Ace SPD pedals. Paint and decals are faded/soft, but the frame is fully chromed underneath and in excellent condition otherwise.