At LGB the spring is seperate from the hook. On the boom of the coupling the spring is connected with a screw. Playmobil was a little more clever in making the hook and spring one part, so connecting with a screw was not neccesary. The Playmobil system has one disadvantage: if the spring is broken, you need to replace the hook as well. The newer Playmobil couplings has a counter balance, that is less prone to damage.
Best is to replace the current old fashioned couplings on your car with a old fashioned hook with spring.
By the way: both type's of Playmobil couplings will perfect connect with the standard LGB couplings.
