Detief,
Worth considering this superb book of Forton's.
It presents 237 high quality photographs of antique navajas, Spanish, and others. The captions are in Spanish but at the back of the book these are reproduced in English:
http://www.libreriagaudi.com/navajas...colecci%C3%B3n
If you shop around, you may get it at a better price.
Cheers
Chris