Denim Button Down fitted shirt

this is almost a faux(?) denim? its soft and stretchy but looks like denim fits a true medium up to a large. Has a nice fitted silhouette but can definitely be tied up for a cute 50s look purchased from Windsor years ago IN GREAT CONDITION the only flaw id say its normal wear.. which wasn't worn too much to begin with BUST 15", LENGTH 22" (pls refer to pics)