After investigating the dataset, it appears that there are indeed 51 unique state identifiers present. However, this is a deviation from the expected since the United States has 50 states. Notably, the District of Columbia (DC) is included in the list alongside the 50 states, which might explain the count of 51 unique "states."

**Issue 1:**
- **issue**: "51 unique states in dataset."
- **evidence**: "Array of unique state identifiers includes: 'AK', 'AL', 'AR', ... 'DC', ... 'WY'."
- **description**: "The dataset contains an entry for 'DC', which stands for the District of Columbia. Including DC with the 50 U.S. states raises the count of unique state identifiers to 51. This inclusion could be misleading or incorrect, depending on the context of the data and how 'state' is defined for this dataset's purposes. It's crucial to clarify whether the dataset aims to represent locations within the 50 states only or intends to also include U.S. territories or districts like DC." 

This clarification is essential to align with the <hint> provided, as it highlights the presence of what might be considered an 'extra' state due to the inclusion of the District of Columbia.