The Rembrandt Group then acquired the building and Dr Rupert undertook to have it restored and converted into an art museum on condition that a sufficient number of South African artists would donate for this purpose an example of their best work. This appeal, made in personal letters, had an immediate and enthusiastic response.
On 26 July 1966 the art museum, with a total of 90 paintings and sculptures donated by 83 artists, was opened by the then State President, Mr C.R. Swart, and given in perpetual trust to the Town Council of Graaff-Reinet. In gratitude, the Council named the museum the Hester Rupert Art Museum in honour of Dr Rupert's late mother. The building was declared a ntional monument on 4 October 1968.
Since then, more artists have donated works to the museum and to date the collection comprises 126 works by 106 artists. Most of the collection is devoted to works produced by artists working in the 1960's who responded positively to the call to save the building for posterity. This collection should not be regarded as representative of 20th Century South African artists but rather as a small, focused collection, as which it remains highly significant.