Knowing what can be doubled helps the search a lot. The single squeeze dies create a different type of doubled die than the older three or more step hubbing process. The multi-hubbed dies have a taller profile than the single squeeze dies have. Look at a current coin and an 1960's cent and check the height of the bust height differences? Then you will see how much higher the profile is on the multi-hubbed dies. So when searching, you look more on the outside edge devices on the multi-hubbed coins and more in the center parts of the single squeeze dies. Which is which?, Look at the profile height of the bust. That will tell you which one it is.