# Relationship history for MSHA mine 1518210

Current hierarchy: **William W  Burton → Burton Stone → Burton Stone**

- 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:** William W  Burton → Burton Stone; 1993-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Burton Stone → Burton Stone; 1999-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William W  Burton → Burton Stone; 1999-10-01 to current/open; source msha-controller-operator-history