My take is that it's NOT the same coin and you'd be justified in returning it on those grounds. There are many many signs that get my suspicions going, but here's just three:
1. the teeth on the right coin (from the V anti-clockwise to the left hand edge of the bust) are thin compared to the greater wear on the left hand coin
2. the totally different style of the JEB - particularly the E which is curved like a reversed 3 on the left, and a normal E on the right, sloping to the right
3. the upper knot on the pendant ribbon has a complete incuse line on the right, which can barely be seen at all on the left.
Add to that the scratch on the last A of GRATIA (not present on the left), and a faint doubling of the ear lobe on the right, and I'd say you've been the victim of possible malpractice.