Self-correcting abacus
The broken lines depict environmental subject matter only and form no part of the claimed design.
Claims
The ornamental design for a self-correcting abacus, as shown and described.
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Type: Grant
Filed: Jun 8, 2006
Date of Patent: Aug 4, 2009
Assignee: Addacus Limited (Leeds)
Inventor: Celia Anne Stone (Leeds)
Primary Examiner: Caron Veynar
Assistant Examiner: Garth Rademaker
Attorney: Austin Rapp & Hardman
Application Number: 29/247,261