This is a Rotring compass attachment. I looked it up, and the part number appears to be 533345. I found it while organizing my house. My family used it for drafting. I don't plan to use it in the future, so I'm listing it in case someone else can use it. It's small, so I will wrap it in cushioning material, put it in an envelope, and ship it via standard mail. If it's during the "Ultra Mercari Sale" period, I can also ship it via Nekopos. Thank you very much.