Better understanding manual reverse engineering can make it and any associated systems reengineering more effective. We reverse engineered a version of a system (referred to as "BOS/X") in support of a broader reengineering effort. System reengineering goals and other circumstances dictated a focused, limited duration, manual reverse engineering exercise. This presented an opportunity to study the BOS/X reverse engineering separately from other reengineering activities. We studied the BOS/X reverse engineering, the results achieved, and some limited reverse engineering metrics. This paper describes the: systems reengineering context; circumstances preventing application of automated techniques and motivating manual reverse engineering; reverse engineering process developed; BOS/X reverse engineering goals; evolution of the reverse engineering products; reverse engineering results; resources required to produce the results; and an evaluation of the reverse engineering effecti...