In paying attention to the tractive effort of locomotives, I've realized I need to know more about coupler strength. I've heard of large early 20th century locomotives pushing the limits of the couplers in use at the time, suggesting they were much weaker than modern couplers. I've read inconsistent statements on the strength of modern couplers. So, what are the strongest couplers in use today? When were couplers of a given strength introduced and withdrawn from service?
