A scope which is for viewing a selected portion of the internal surface of a bore or similar cavity and which includes a viewer of optically clear light transmitting material and a housing. The viewer is encased within a longitudinal bore of the housing with its viewing end adjacent the upper end face...http://www.google.com/patents/US4373811?utm_source=gb-gplus-sharePatent US4373811 - Scope for viewing the internal surface of a bore or similar cavity
