▁H als ▁group ▁port ra its ▁in ▁H aar lem . ▁ ▁United ▁States ▁After ▁working ▁with ▁G oup il ▁& ▁C ie ▁in ▁Paris , ▁Care l ▁received ▁an ▁offer ▁to ▁work ▁as ▁an ▁ad visor ▁and ▁rest orer ▁with ▁art ▁dealing ▁institution ▁Kno ed ler ▁& ▁Co , ▁and ▁depart ed ▁for ▁the ▁United ▁States ▁in ▁ 1 9 1 1 . ▁During ▁his ▁time ▁with ▁Kno ed ler ▁& ▁Co ., ▁and ▁subsequently ▁at ▁the ▁independent ▁practice ▁on ▁Fif th ▁Avenue ▁he ▁opened ▁in ▁ 1 9 1 6 , ▁he ▁worked ▁closely ▁with ▁American ▁industrial ists ▁Henry ▁Clay ▁Fr ick , ▁Joseph ▁W id ener , ▁and ▁J . P . ▁Morgan . ▁He ▁ad vised ▁Fr ick ▁on ▁several ▁major ▁art ▁purch ases ▁in ▁the ▁ 1 9 1 0 s , ▁including ▁V erme er ' s ▁M ist ress ▁and ▁Ma id , ▁Gilbert ▁Stuart ' s ▁portrait ▁of ▁George ▁Washington , ▁and ▁a ▁Jacob ▁Mar is ▁landscape , ▁later ▁rest oring ▁Fr ick ' s ▁pri zed ▁Rem brand t ▁self - port rait . ▁Well - known ▁as ▁the ▁first ▁to ▁bring ▁the ▁so - called ▁" D utch ▁method " ▁of ▁w ax - res in ▁l ining ▁outside ▁the ▁Netherlands , ▁he ▁was ▁called ▁in ▁by ▁a ▁government ▁art ▁app ra iser ▁to ▁give ▁his ▁expert ▁opinion ▁on ▁a ▁case ▁of ▁sus pected ▁art ▁fra ud ▁in ▁ 1 9 1 6 . ▁A ▁firm ▁pro ponent ▁of ▁investig ating ▁the ▁physical