# Relationship history for MSHA mine 4801443

Current hierarchy: **Koppers Co Inc & Redland Plc → Sterling Sand & Gravel Company Of Wyoming → North 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

- **controller_controls_mine:** Koppers Company Inc → North Pit; 1981-11-15 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sterling Sand & Gravel Company Of Wyoming → North Pit; 1985-10-01 to 1987-07-28; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Sterling Sand & Gravel Company Of Wyoming; 1985-10-01 to 1987-07-28; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Co Inc & Redland Plc → North Pit; 1987-04-20 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sterling Sand & Gravel Company Of Wyoming → North Pit; 1987-07-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Co Inc & Redland Plc → Sterling Sand & Gravel Company Of Wyoming; 1987-07-29 to current/open; source msha-controller-operator-history