# Relationship history for MSHA mine 0501038

Current hierarchy: **Koppers Company Inc → Sterling Sand & Gravel Company → Johnson 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Sterling Sand & Gravel Company → Johnson Pit; 1950-01-01 to 1981-11-14; source msha-controller-operator-history
- **controller_controls_mine:** Sterling W A → Johnson Pit; 1950-01-01 to 1981-11-14; source msha-controller-operator-history
- **controller_controls_operator:** Sterling W A → Sterling Sand & Gravel Company; 1950-01-01 to 1981-11-14; source msha-controller-operator-history
- **operator_operates_mine:** Sterling Sand & Gravel Company → Johnson Pit; 1981-11-15 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Johnson Pit; 1981-11-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Sterling Sand & Gravel Company; 1981-11-15 to current/open; source msha-controller-operator-history