rdmadison - Since I have cleaned, aligned, disassembled, etc. a number of Zephrys over the years, my comments are from experience. The American B&L binoculars have always rivaled Zeiss in terms of quality of materials and workmanship. Coatings on the Zephyrs appeared during the WWII era, or shortly thereafter. B&L coatings are relatively soft and easily rubbed or marred. But that has little effect on opitcal image. Japanese coatings are very hard when compared to the B & L on the other hand.
Any center focus binocular with the oculars moving up and down will create a bellows effect, and will bring in impurities into the system. Over the years this often creates a light haze on the prisms, lessening the inherent brightness of the optical system. B&L tolerances are very precise, and the stiffness when focusing is the function of three areas where friction can arise because of lubricant breakdown and pieces of grit
1) the center screw assembly which moves the oculars up and down, (2) where the bridges hold the ocular assembly which move in and out, and (3) the tubes housing the oculars which in turn slide inside the main tubes which thread through the shelves or lids into the body or chassis itself.
Individual focus binoculars have minimal bellows effect and are tighter. Hence, they tend to survive the ravages of times due to dust, water, and grit. My experience with CF Zephyrs demonstrates that most of the "stiffness" is found between the two tube assemblies. Tiny pieces of grit can migrate to the edges of the tubes and create galling which has a disproportionate effect on negating smooth movement when the center wheel is turned. As mentioned before, B&L tolerances are precise but tight. Tight enough to aid in collimation but loose enough to allow lubricants to help the ocular tubes move with ease. Sometimes the gunk is so thick the tubes seem almost frozen.
But they aren't and can be carefully moved apart for cleaning. Often the minute galling leaves tell tale marks lengthwise on the tubes.
Whom to send to? A number of folks do that kind of work. But don't be surprised if the cost is high. For do it your self kinds of folks, appropriate screw drivers, strap wrenches, and lens cleaning materials are essential as is a surgically clean work area.
Becoming familiar with the mechanical processes is helpful - tear into a junker binocular first. Then proceed with caution. If you do "break into " a B&L Zephyr, you will quickly understand the precision and quality which made it a standard of the industry over fifty years ago. John
