13. Stamp printed on both sides: What is referred to here are "positive" prints on both sides caused either by a lack of care on the part of the printer or by printing on the back of waste that should have been destroyed. These are usually seen on the Banknote issues of 1851 to 1883 and are very rare and pricey.
Type 13: This figure depicts a pair of Scott 65e printed on both sides of the paper. Top: Front. Bottom: Reverse.