I see no reason to suspect foul play here. The Mamaea and the Tranquillina were swapped. The exhibit may have been correct once but the coins fell loose or were removed for study and replaced incorrectly by someone who simply did not care. After all, these are just coins and museums have 'real' art.
Agreed! I don’t see how there could be foul play. To my knowledge, the coins involved aren’t particularly valuable. You’re probably right that they were removed and subsequently swapped because they’re actually correctly labelled on the museum’s website.