Mathematical aid
Description
FIG. 1 is a top perspective view of a mathematical aid showing our new design; and
FIG. 2 is a bottom plan view thereof.
Referenced Cited
U.S. Patent Documents
| D217770 | June 1970 | Goldberg |
| D231738 | June 1974 | Brass |
| D241856 | October 1976 | Williams |
| D265666 | August 3, 1982 | Nakao et al. |
Patent History
Patent number: D317787
Type: Grant
Filed: Feb 21, 1990
Date of Patent: Jun 25, 1991
Inventors: William A. Davidson (Perth), Silvia Davidson (Perth), John D. Charters (Midland)
Primary Examiner: Wallace R. Burke
Assistant Examiner: P. Schmidt
Law Firm: Harness, Dickey & Pierce
Application Number: 7/482,749
Type: Grant
Filed: Feb 21, 1990
Date of Patent: Jun 25, 1991
Inventors: William A. Davidson (Perth), Silvia Davidson (Perth), John D. Charters (Midland)
Primary Examiner: Wallace R. Burke
Assistant Examiner: P. Schmidt
Law Firm: Harness, Dickey & Pierce
Application Number: 7/482,749
Classifications
Current U.S. Class:
Demonstrator Or Exhibitor (10) (D19/62)
