# Relationship history for MSHA mine 1508285

Current hierarchy: **Brock Ramsey → H B H Coal Co Inc → Dartmont 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

- **operator_operates_mine:** H B H Coal Co Inc → Dartmont Mine; 1975-04-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Brock Ramsey → Dartmont Mine; 1975-04-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Brock Ramsey → H B H Coal Co Inc; 1975-04-21 to current/open; source msha-controller-operator-history