| title | ISBN-13 (ISBN-10) | year of publica- tion | other author(s) |
|---|---|---|---|
| Patek Philippe: Wrist Watches, Pocket Watches, Clocks: Identification and Price Guide: Retail & Vintage Prices: Book 1 | 978-0-913902-60-8 (0-913902-60-8) | 1991 | Roy Ehrhardt |
| Vintage American & European Wrist Watch Price Guide: Book 4 | 978-0-913902-58-5 (0-913902-58-6) | 1989 | Sherry Ehrhardt · Roy Ehrhardt · Peter Planes · David A. Mycko |
| Vintage American and European Wrist Watch Price Guide/Book 2 | 978-0-913902-56-1 (0-913902-56-X) | 1988 | Sherry Ehrhardt · Roy Ehrhardt · Ken Specht · Peter Planes · David A. Mycko |