Ticker DD
From 2019-06-01 00:00:00
Security Type Equity
Market USA
Resolution Daily
Status In progress

On 2019-06-01 DWDP changed symbol to DD and did a reverse split (

https://seekingalpha.com/pr/17523522-dowdupont-stockholders-approve-reverse-stock-split-board-of-directors-determines-reverse

The symbol change appears to be tracked in the data, but the split is not.