# Relationship history for MSHA mine 0504172

Current hierarchy: **Redland Plc → Sterling Sand & Gravel Company → Challenger**

- 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:** Koppers Co Inc & Redland Plc → Challenger; 1950-01-01 to 1988-06-13; source msha-controller-operator-history
- **operator_operates_mine:** Challenger Gravel Pit Partnership → Challenger; 1986-08-01 to 1987-05-21; source msha-controller-operator-history
- **controller_controls_mine:** Challenger Albert S & Jerry E Klein → Challenger; 1986-08-01 to 1987-05-21; source msha-controller-operator-history
- **controller_controls_operator:** Challenger Albert S & Jerry E Klein → Challenger Gravel Pit Partnership; 1986-08-01 to 1987-05-21; source msha-controller-operator-history
- **operator_operates_mine:** Sterling Sand & Gravel Company → Challenger; 1987-05-22 to 1988-06-13; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Co Inc & Redland Plc → Sterling Sand & Gravel Company; 1987-05-22 to 1988-06-13; source msha-controller-operator-history
- **operator_operates_mine:** Sterling Sand & Gravel Company → Challenger; 1988-06-14 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Redland Plc → Challenger; 1988-06-14 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Redland Plc → Sterling Sand & Gravel Company; 1988-06-14 to current/open; source msha-controller-operator-history