Of the instances I know of most one-off's never were from an assembly line just attempts to change or demonstrate a concept. The R&D group I worked with always was producing prototypes and proof-of-concept devices. The proof-of-concept units were mostly breadboard style with wires and components in any order and not in any form factor. A prototype was then constructed, sometimes milled of plastic or aluminum, it mimicked the final units appearance. The prototypes went through several interations to make a manufacturable model that could be made within the cost desired. Then the manufacturing engineers came in and tried to make it repairable and assembleable. The whole process is currently much compressed with the manufacturing engineers included from the beginning to reduce cost and time-to-market. Our group made medical microbiology devices designed by aerospace engineers, way overengineered, and with more feedback sensors than you could believe. We started out with PDP 11/05 , then migrated to 11/04. They eventually wanted to replace our PDP-11/04, with VT52, based computer systems with homegrown computer, terminal, and printer. Never implemented. Mike mmcfadden(a)cmh.edu