This is the stamp which may or may not have the variety.

Could anyone post a better image of this variety than is in the current Unitrade catalogue. Does it match my specimen? I am assuming for the present that the variety relates to the harness from the second right dog where it disappears behind the rightmost dog, based on Unitrades further description of the of the variety as "black thread",
Unitrade does not list its position on the sheet but does indicates (presumably) that the variety appears on a Plate Block. I have all four corners as Plate Blocks. While Unitrade says it was printed in panes of 50, it does not show how may stamps/panes were printed in the sheet. It is thus possible that I do not have have the variety in my four PBs.