37. Lines of perforations partially missing: This was initially caused by damage to the perforating wheel. In more recent times, it resulted from perforating mechanisms engaging or disengaging at the start or end of production, or for other reasons. Value varies with the item affected and the degree of the problem but only really unusual examples exceed $25.
Type 37: Examples of partially missing perforations: Left: Scott 899, right: Scott 1581.