French term (edited): cabinet d\'expertise (d\'art)

according to the context presented

In such contexts, "surveyor" and "valuer" are used, and art is no exception.

http://www.paulbritton.com/

Paul Britton Art Surveyor and Valuer
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an image of an abstract painting
Paul Klee (1879-1940)
Hauser Mit Baumallee, 1915
Watercolour

Independent Art Claims Consultancy
Paul Britton MRICS FRSA is a Chartered Arts and Antiques Surveyor providing independent art appraisal and claims consultancy services to the Fine Art insurance market, legal profession and those transacting in art. Principal clients include leading art insurance companies, brokers, legal advisors, private collectors and institutions.

Worldwide Post-Loss Appraisal
Post loss appraisal and valuation reports following damage, loss or theft are provided for all categories of art objects. Services are rendered worldwide, principally in connection with insurance claims for art dealers, galleries, auction houses, private collectors and museums.

Expert Reports For All Categories of Works of Art
Expert reports are provided to the legal profession for the purposes of litigation involving Works of Art. Advice given draws upon many years of expertise in art appraisal and valuation and wide experience in art market practice, including conservation and restoration. In 2011 Paul secured, in association with OmniArte, Switzerland, a commission to catalogue and value the art collection holdings of the European Parliament, Brussels and Luxembourg.

Risk Management and Collection Care
A bespoke risk management and collection care service provides access to leading practitioners in the fields of conservation, framing, installation, transportation and storage, art law and other ancillary services.