Most of the 2¢ stamps are thankfully different and can be identified by the size of the perforations and in a couple of instances if they are type I or type II. However there are two stamps that confuse most folks #595 and #554. Scotts give the measurements of these stamps, which are incredibly hard to measure, I have shown how below. As you can see below the difference is very small and where you place the first notch in the ruler has to be dead accurate the “0” line on the gauge goes flush with the start of the design. By far the easiest method is to purchase a cheap and cheerful #599 and compare the two stamps against it as shown below. Note that I have cut the corners off #599 in order to make it easier to line the stamps up.