# Relationship history for MSHA mine 2500056

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta Aggregates → Marion Portable #873**

- 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:** Hopper Brothers Quarries → Marion Portable #873; 1950-01-01 to 1980-08-07; source msha-controller-operator-history
- **controller_controls_mine:** Hopper Chester & Raymond → Marion Portable #873; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hopper Chester & Raymond → Hopper Brothers Quarries; 1950-01-01 to 1980-08-07; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → Marion Portable #873; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Aggregates → Marion Portable #873; 1980-08-08 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Aggregates; 1980-08-08 to current/open; source msha-controller-operator-history