# Relationship history for MSHA mine 3303601

Current hierarchy: **Mason Russel & C R → Mason Coal & Gravel → Mason Coal Prep Plant**

- 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

- **operator_operates_mine:** Mason Coal & Gravel → Mason Coal Prep Plant; 1977-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Mason Russel & C R → Mason Coal Prep Plant; 1977-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mason Russel & C R → Mason Coal & Gravel; 1977-04-01 to current/open; source msha-controller-operator-history