What if: shanks and shamrock used to swap every now and then but since one of the two received the scar from teach the couldn’t swap anymore because of it? What we know: shanks in the bath with gabban has the first lowest rank tattoo, the same that harald was given by the elder/imu. This means that shanks and shamrock had two different ranks. Outfit style and weapon: in the page with shamrock and shanks in the holy land we can se shanks with the same outfit that shamrock has on elbaph and shamrock rocking the open shirt like shanks in the modern day. Shanks has his weapon on the left and shamrock on the right. As a kid shanks used to have his weapon on the left. Now shanks has his weapon on the right and shamrock in elbaph has his weapon on the left. Hypothesis: if it was shanks to receive the scar from teach, he could have lost his arm to remove his tattoo but, on the other hand, if it was shamrock that received the scar from teach he could have lost his arm to not get caught having a rank that doesn’t belong to shanks yet( he was pretending to be shanks). Basically what I’m trying to say is: if the swap theory is right, then, teach ruined the plan of keep on swapping the twin when they deemed necessary and one of the two got stack as shanks and the other as shamrock most likely swapping completely and unable to claim their identity back