Koetser is a major dealer in Old Masters and Founder Member of The European Fine Art Fair (Tefaf) in Maastricht, The Netherlands. Over the last century many U.S.Museum have purchased from the Koetser Gallery as well as European Museums and Private Collectors. The Gallery has handled great paintings by Rubens, Frans Hals, Aelbert Cuyp, Jan van der Cappelle (now Getty Museum). A painting by Jan Lievens sold in recent years is now on loan to the National Gallery, Washington. David Koetser likes to present paintings to the public. Exhibitions and lectures have been annual events and Old Masters from the Koetser Foundation may be seen in the Zurich museum ‘Kunsthaus’.