Emperor Aurelian (270-275) did his utmost to turn the Roman Empire from the crisis of the 3rd century. He also improved the quality of coins. Their weight and size met the standards again, even though the state was not yet in a position to raise the silver content.
This antoninian was struck after 271 AD. That was the year in which a revolt broke out in Rome that cost the lives of more than 7000 people. A mint official commanded it, although for the reasons we have no clues. This apparently led to the exchange of the mint's whole team, as becomes obvious by the style of the coins, which changed so drastically in 271 that we have to conclude that they where made by an entirely new group of workers.