A closer look is often needed. It's probably a different sweetheart. A good place to start looking is the hole where the crank drive pin goes, and all the other possible locations for that hole. You will probably start to see differences there, and in other hole shapes too.
Also always pay attention to whether it is 1/2" or 1" pitch. All the Schwinn sweethearts are 1" pitch, and so it this Colson, so it wont help in this case, but sometimes it does.