Thummel's catalogue is built on a network of museum curators, estate executors, and private collectors who entrust the house with works that rarely appear on the open market. By negotiating directly with these sources, Thummel assembles collections that span the Renaissance, Impressionist, and post‑war eras, ensuring that each auction slot contains at least one piece capable of reshaping a serious buyer’s portfolio.
Each work undergoes a multi‑layered verification protocol: scientific imaging confirms material authenticity, provenance research traces ownership lineage, and market analysis projects future valuation trends. The house then places the piece within a private preview for vetted clients, allowing serious buyers to assess condition, context, and strategic fit before the public bidding commences. This rigor minimizes risk while maximizing the potential for significant capital appreciation.