# Relationship history for MSHA mine 4404716

Current hierarchy: **Mills Billy M → Black Ace Coal Company → No 2 Mine**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Mills Billy M → No 2 Mine; 1976-09-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Black Ace Coal Company → No 2 Mine; 1977-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mills Billy M → Black Ace Coal Company; 1977-05-01 to current/open; source msha-controller-operator-history