| Number | Name | Date | Kind |
|---|---|---|---|
| 2607649 | Johnson | Aug 1952 | |
| 3587453 | Klein | Jun 1971 | |
| 3921539 | Berger | Nov 1975 | |
| 4872733 | Tedham et al. | Oct 1989 |
| Entry |
|---|
| Three Copies of Photographs of bottom of IBM PS/2 Model 80 Unit. |
| AST Computers Advertisement in PC Week, Feb. 19, 1990, pp. 68-69. |
| ALTEC Technology Corp., Advertisement in INFOWORLD, Feb. 5, 1990, p. 88. |
| Sys Technology, Inc., Advertisement in PC Week, Feb. 12, 1990, p. 100. |
| USM Distributors Advertisement in PC Week, Feb. 19, 1990, p. 111. |