It's a Takagi [Three Arrows] crank. They were based in Osaka Japan. I believe they made the early Tourney and Dura Ace cranks for Shimano. Perhaps someone on the List can confirm or refute this. Mainly they seem to have made low end "swaged" type cotterless and steel cottered cranks. Yours is beautiful and i would guess mid '60s, but perhaps earlier. Billy Ketchum; Chicago, IL; USA.