Peter Kidd’s blog Medieval Manuscripts Provenance was for years perceived as a niche tool for tracing manuscript ownership. However, a closer examination of its structure, purpose, and use by dealers reveals that the blog often functioned as an amplifier for the commercial circulation of excised leaves — folios removed from illuminated manuscripts and sold individually on the antiquarian market. The blog, which has not been updated since early 2023, lacked any formal peer-rev