This is a Rotring 600 ballpoint pen, an older model with a rare color indicator window. The logo has faded, but the knurled grip has minimal dirt and is in excellent condition. I believe it looks better this way than with a partially faded logo. Operation has been confirmed, and the color indicator window is also clean. The original black ink loaded in it writes. It accepts current G2 refills. I purchased this on Mercari for around 10,000 yen some time ago. Thank you.