# Relationship history for MSHA mine 3606476

Current hierarchy: **Fishburn Harry W-Bruce & Leonard → Hard Rock Coal Company → Skidmore Slope**

- 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

- **operator_operates_mine:** Hard Rock Coal Company → Skidmore Slope; 1977-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Fishburn Harry W-Bruce & Leonard → Skidmore Slope; 1977-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Fishburn Harry W-Bruce & Leonard → Hard Rock Coal Company; 1977-08-01 to current/open; source msha-controller-operator-history