# Relationship history for MSHA mine 0100421

Current hierarchy: **Robbins Coal Company → Robbins Coal Company → Robbins Strip 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:** Robbins Coal Company → Robbins Strip Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Robbins Coal Company → Robbins Strip Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robbins Coal Company → Robbins Coal Company; 1950-01-01 to current/open; source msha-controller-operator-history