Perhaps they are sour oranges, it is the variety that is produced in some countries, they use them for what you say, jams, even a kind of lemonade, but with orange for its flavor, also when people are cold, the important thing is that they are not they let lose, I hope that there they learn to value them
You are right. The oranges are too sour and can be used for making marmalade only. Maybe some people make marmalades from them, but there are too many orange trees.