# Relationship history for MSHA mine 0504509

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta Materials Inc. → Penrose Ranch Gravel Pit**

- 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

- **controller_controls_mine:** Martin Marietta Materials Inc → Penrose Ranch Gravel Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Stephen  Schnurr → Penrose Ranch Gravel Pit; 1990-11-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Rocky Mountain Materials & Asphalt Inc → Penrose Ranch Gravel Pit; 1992-12-01 to 2016-03-03; source msha-controller-operator-history
- **controller_controls_operator:** Stephen  Schnurr → Rocky Mountain Materials & Asphalt Inc; 1992-12-01 to 2016-03-03; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Materials Inc. → Penrose Ranch Gravel Pit; 2016-03-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Materials Inc.; 2016-03-04 to current/open; source msha-controller-operator-history