As you can see in the written portion, this is a TWSBI Diamond 540 Clear + 1.1mm stub nib. It's inked with J. Herbin Rouge Hematite anniversary ink. (This text is for Google searching purposes, mostly!)
I believe the 1.1mm stub nib is no longer available for purchase, so if you find it, you better pick it up. And the other colors are on the go too, on close out prices of $40.00!