| Number | Name | Date | Kind |
|---|---|---|---|
| 2560624 | Bartlett | Jul 1951 | |
| 2963895 | Thomas | Dec 1960 | |
| 3677259 | Reque et al. | Jun 1972 | |
| 3889497 | Tuttle | Jun 1975 | |
| 4085599 | Fischer et al. | Apr 1978 | |
| 4409804 | Sork | Oct 1983 | |
| 4864834 | Waite | Sep 1989 | |
| 5020342 | Doan et al. | Jun 1991 | |
| 5167135 | Gobeski | Dec 1992 | |
| 5365757 | Primeau | Nov 1994 |
| Number | Date | Country |
|---|---|---|
| 346278 | Dec 1921 | DEX |
| 175600 | Mar 1935 | CHX |
| Entry |
|---|
| "Safety Lockouts," Hoffman Engineering Company advertising brochure, p. 507, 1995. |
| Sketch of lock holder dated May 27, 1993. |