Robin Mazz

I have a pair of Caiman Lizards for 4 years. I bought them as adults and the guy who sold them to me thinks they are a sexed pair. He was not sure. Both have the same coloration and the heads seem to be the same shape. I have no way of comparing to other animals of the same age unless I buy another animal or bring the animals to someone else who has them also. I understand I can have a vet take blood but i don't want to spend the money unless I have to. Plus these animals don't appreciate being handled. These animals have always gotten along and I don't want to bring another animal into the mix unless I can trade someone for one of mine and we are both sure we have animals of the opposite sex...I have seen pictures of other animals with blunter heads but again I'm not sure...Does anyone have any suggestions??