| Number | Name | Date | Kind |
|---|---|---|---|
| 149958 | Smith | Apr 1874 | |
| 567231 | Glauber | Sep 1896 | |
| 925762 | Eager | Jun 1909 | |
| 2086007 | Tompkins | Jul 1937 | |
| 2215318 | Bristol | Sep 1940 | |
| 3222777 | Rutter et al. | Dec 1965 | |
| 3825288 | Maroschak | Jul 1974 |
| Entry |
|---|
| Brochure of Northern Pipe Products, GPK Products, Inc., undated but admitted to be prior art, not dated. |