Thank you! I did read the PDF, it just isn't setting in! This helps though.Yes, they are called knuckle couplers, and they are what most people use these day. of all the brands out there, Kadee is the best known and has the widest selection.
As for your spares, just from your description it sounds as though they may be Kadee #5's, which were probably the most widely used knuckle couplers until the whisker style (with the two 'arms') came into being.
The reason they get off to one side is that they don't have a built in centering spring. The springs are available from Kadee
They mount in the coupler box on top of the coupler. A small puff of powdered graphite lubricant helps operation. Don't use oil or grease in the couplers, it attracts dirt. Once installed, the #5's will work fine with the whisker style couplers.
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