Nicolaus Knupfer

Probably, C.P. Henry;
Probably, his sale, Paris, Michalon, 30 March-4 April 1818, lot 158 (as N.Knufer [sic.], where called "Saint Thomas doutant de la résurrection de Jésus-Christ, s'en assure en mettant le doigt dans sa plaie"), to Sibire.

Possibly J. Saxton, Nicolaus Knupfer, Doornspijk 2005, p. 244, cat. no. D-C 6 (where listed under Unidentified References: Drawings).

Though not officially published in Jo Saxton's 2005 monograph on Knupfer, this may be the picture which Saxton refers to amongst the works which are linked to unidentified references. One of these works is a Doubting Thomas which is mentioned by Hofstede de Groot, and was sold at Michalon in Paris in 1818, as the property of C.P. Henry.