So far we only know of the following marked with IH:
2 Sucket spoons of almost identical appearance
1 set of 6 brightcut teaspoons
Both the sucket spoons are marked with a duty mark and a letterbox lion:
My teaspoons are marked with the same sideways duty mark but with a wavy bottomed lion. If only the Exeter records existed for the unusual sucket spoons it would give us a more accurate date but maybe the sideways punching of the duty mark will appear on some larger silver that can be dateable to a year period.