As one of the effective practices of software quality assurance, peer code review is sometimes not able to work as expected. In order to reinforce the quality of code delivery, especially to improve future coding quality, one global Information and Communication Technology (ICT) enterprise has institutionalized a retrospective style inspection (namely retro-inspection), which is similar to Fagan inspection but differs in terms of purposes, stage, participants, etc. This paper reports a case study that aims to investigate the experiences and lessons from this software practice in industrial settings. To this end, we collected and analyzed various empirical evidence for data triangulation from a long-term observation. The results indicate that retro-inspection distinguishes itself from peer code reviews by identifying more complicated and underlying defects as well as providing more indicative and suggestive comments. Many experienced inspectors indicate defects together with their rationale behind and offer suggestions for correction and future prevention. As a result, retro-inspection is able to benefit not only quality assurance (like Fagan inspection), but also internal audit, inter-division communication, and competence promotion. On the other side, we identify a series of lessons of retro-inspection at this stage, e.g., developers’ disagreements and organizers’ confusion, for improvement of this practice. To be specific, some recommendations are discussed for retro-inspection, including entrance threshold and publicity policy. This study concludes that most of the expected benefits of retro-inspection can be empirically confirmed in this enterprise and its value on the progress to continuous maturity can be recognized organization-wide. The experiences on executing this altered practice in a large enterprise provide the reference value on code quality assurance to other software organizations.