Can You Identify This Sharpening Related Item?

Can you guess what this is and what it's used for? Hint: It's really heavy! We'll post the answer tomorrow.

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To whom it may concern, I got my DMT Aligner Kit today and I just cant say enough about it and my experience with I got the extra extra fine stone along with the DMT deluxe aligner kit. My favorite knife now is as sharp as a scalpel. First Class Company and First Class Products. Truly a pleasure doing business with you.
Richard O, El Cajon, CA