Those photos of yarrelli's make my heart ache a little. That of course is the reason why the modern sealed roof prism binocular is so much preferred by most birders. In the past there were more technicians that could clean and service binoculars (I often think the affection many of them profess for unsealed porros might have had something to do with that type of binocular keeping them in business!) but they are, alas, few and far between now.