# Relationship history for MSHA mine 1518959

Current hierarchy: **Robert C  Billips → Peter Fork Mining Company → No 1 Elkhorn**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Robert C  Billips → No 1 Elkhorn; 1974-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Peter Fork Mining Company → No 1 Elkhorn; 2006-01-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert C  Billips → Peter Fork Mining Company; 2006-01-13 to current/open; source msha-controller-operator-history