What does the JJT mean

In the USA the Federal Trade Commission regulations require a jeweler to include a maker's mark (or trademark) along with a hallmark. The hallmark indicates the specific gold content... in your case 10 karat gold and the maker's mark (trademark) accompanying it (JJT) indicates it was made by J.J. Creations of New Jersey, USA.

Sources:

1) http://www.jewelry-design-gemstone.com/real-gold.html

2) http://www.trademarkia.com/jjt-85028424.html