Physical description: circular patch of chemical sensitising
Inscription: in ink, verso, April/39 [April 1839]; in pencil, verso, A
Watermark: hat
Watermark (expanded): Whatman
Provenance: Victoria & Albert Museum, 2017 National Science and Media Museum, 2003 to 2017 Royal Photographic Society, number 025107 Royal Photographic Society, previous number 223