| Number | Name | Date | Kind |
|---|---|---|---|
| 1209350 | Steiner | Dec 1916 | |
| 1232782 | Field | Jul 1917 | |
| 1384389 | Johnson | Jul 1921 | |
| 1770045 | Shore et al. | Jul 1930 | |
| 1973333 | Craemer | Sep 1934 | |
| 2448486 | Chester | Aug 1948 | |
| 2466567 | Williams | Apr 1949 | |
| 2643544 | Chester | Jun 1953 | |
| 2693698 | Scott | Nov 1954 | |
| 2835127 | Scott | May 1958 | |
| 2976723 | Eddy | Mar 1961 | |
| 3128621 | Scott | Apr 1964 | |
| 3129582 | Borgersen | Apr 1964 | |
| 3138951 | Scott | Jun 1964 | |
| 3486373 | Scott | Dec 1969 | |
| 3754436 | Saxton | Aug 1973 | |
| 4036048 | Webster | Jul 1977 | |
| 4094188 | Bellouin et al. | Jun 1978 | |
| 4147052 | Tsujiuchi et al. | Apr 1979 |
| Number | Date | Country |
|---|---|---|
| 2357755 | Jun 1974 | DEX |
| 2751095 | Mar 1979 | DEX |
| Entry |
|---|
| Introdyne Universal Horizontal Hardness Tester, (Blue River Laboratories, R.D. #4, Box 76, Lewistown, Pennsylvania 17044). |
| Hirth Minimeter for Accurate Measuring, (Falkimer Machinery Co. Pty, Ltd., Famacoy House, Goulburn Street, Sydney, Australia). |