During the 2014-2015 restoration of the Hall of Mental Cultivation (Yangxin Dian) in the Forbidden City, multiple areas of flaking and loss were discovered on the decorative carvings of the Vairocana Hat (Pilu Mao) Floral Gateway at the junction of the rear hall of the Hall of Mental Cultivation and the “I”-shaped corridor. Concurrently, damage assessment revealed numerous traces of historical repairs on this set of interior eaves. By integrating evidence from the artifact’s current condition with these historical repair traces, it was determined that the interior eaves were originally constructed using a variety of wood species and assembled through different inlay techniques. With reference to comparable artifacts preserved in the Forbidden City, the original appearance of the artifact was visually reconstructed. The restored original appearance revealed a striking contrast between the original decorative appearance and the current uniformly black surface. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis of the surface coating on the interior eaves indicated that animal glue was used as a primer layer, followed by an application of shellac (also known as “insect resin lacquer”) or a shellac-based mixture. Based on these findings, it is thus inferred that the artifact underwent a later alteration involving an overall black coating and that deviated from its original design intent. This study provides valuable reference material for research on Qing Dynasty interior eave craftsmanship, as well as the ritual systems and court culture of the late Qing period.