Issued Patents All Time
Showing 1–3 of 3 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 5326797 | Fire resistant roofing asphalt composition | Harold M. Zimmerman, David Michael Ploense, Robert Lilleston | 1994-07-05 |
| 5169690 | Fire resistant roofing system | Harold M. Zimmerman, David Michael Ploense, Robert Lilleston | 1992-12-08 |
| 5100715 | Fire resistant roofing system | Harold M. Zimmerman, David Michael Ploense, Robert Lilleston | 1992-03-31 |