NGC 1999-P Delaware quarter 2 coin bonded pair, with the obverse coin double-struck and bonded to the bottom coin. The top coin is dramatically double-struck and cupped upwards, while the bottom coin is a reverse die cap that stuck to the reverse die and was struck multiple times into the top coin, bonding them together. 

Bonded state quarters are rare, with probably around 15-20 examples known for state quarters. This is the 1st year of issue for state quarters, and as such, it is a more interesting year to have for a bonded state quarter. An extremely rare opportunity to buy a bonded state quarter, as they do not often come on the market. 

This coin would be the centerpiece of many state quarter error collections!

MS67 lustrous.