 
                 Patent Grant
 Patent Grant
                     6120029
 6120029
                    | Number | Name | Date | Kind | 
|---|---|---|---|
| 3406975 | Berger | Oct 1968 | |
| 3794326 | Bialek | Feb 1974 | |
| 3881731 | Droney | May 1975 | |
| 3908999 | Brown | Sep 1975 | |
| 4079941 | Morales | Mar 1978 | |
| 4927157 | Riihiluoma | May 1990 | |
| 5011159 | Fortunato | Apr 1991 | |
| 5197742 | Bendit | Mar 1993 | |
| 5257787 | Miccio | Nov 1993 | |
| 5275414 | Stephens | Jan 1994 | |
| 5413352 | Persidsky et al. | May 1995 | |
| 5490675 | Persidsky et al. | Feb 1996 | |
| 5536014 | Serfozo | Jul 1996 | 
| Entry | 
|---|
| Petty Chess, published in Sep. 1930 B. Walker Watson issue of the British Chess Magazine. |