# Relationship history for MSHA mine 1500138

Current hierarchy: **Crane Company → Medusa Aggregates Company → Smith Grove Quarry**

- 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:** State Contracting & Materials Division → Smith Grove Quarry; 1950-01-01 to 1978-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Medusa Corp → Smith Grove Quarry; 1950-01-01 to 1979-01-31; source msha-controller-operator-history
- **controller_controls_operator:** Medusa Corp → State Contracting & Materials Division; 1950-01-01 to 1978-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Crane Company → Smith Grove Quarry; 1978-12-13 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Medusa Aggregates Company → Smith Grove Quarry; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Crane Company → Medusa Aggregates Company; 1979-01-01 to current/open; source msha-controller-operator-history