Does this sound in the ballpark?
Ooops might be 180/60 HR 16. The other may just be a model #
180/60 HR 16 XXX
Usually 2 digits for a load rating (and 1 letter for a speed rating). I always go with the highest load rating in the size I want. I was amazed how fast you can overload a tire when riding two up. Factor in the dynamics of weight transfer (even at steady cruise) and it is easy to be over.
Don't know if you saw the thread from a couple days ago. The lesson is... Always replace the valve stem.