Hong Kong SG55d 10c on 30c DOUBLE SURCHARGE in a strip of 3 U/M

1898 (1 Apr) 10c on 30c grey-green type 17 surcharge with additional type 18 Chinese handstamp first printing Strip of three with the middle stamp having a DOUBLE Surcharge. (the second heavier impression spaced 1/3mm to lower right).There are only six recorded examples (originally in a block.) This is the only wing/gutter margin example. The stamps are Un-mounted mint (mint never hinged) lightly toned gum as with all examples. There is a copy of the certificate signed by R.N. Gurevitch when in the block of 36. Ex Alfred M. Chu collection and illustrated and discussed on pp. 46-7 of his 1998 monograph.