# Relationship history for MSHA mine 1800078

Current hierarchy: **Wienerberger AG → Cherokee Sanford Brick → Muirkirk Mine**

- 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

- **operator_operates_mine:** Maryland Clay Products → Muirkirk Mine; 1950-01-01 to 1990-08-30; source msha-controller-operator-history
- **controller_controls_mine:** Borden Brick & Tile Company → Muirkirk Mine; 1950-01-01 to 1990-08-30; source msha-controller-operator-history
- **controller_controls_operator:** Borden Brick & Tile Company → Maryland Clay Products; 1950-01-01 to 1990-08-30; source msha-controller-operator-history
- **operator_operates_mine:** Maryland Clay Products Division → Muirkirk Mine; 1990-08-31 to 2000-02-09; source msha-controller-operator-history
- **controller_controls_mine:** Cherokee Sanford Group Inc → Muirkirk Mine; 1990-08-31 to 2000-02-09; source msha-controller-operator-history
- **controller_controls_operator:** Cherokee Sanford Group Inc → Maryland Clay Products Division; 1990-08-31 to 2000-02-09; source msha-controller-operator-history
- **controller_controls_mine:** Wienerberger AG → Muirkirk Mine; 2000-02-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Cherokee Sanford Brick → Muirkirk Mine; 2000-02-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Wienerberger AG → Cherokee Sanford Brick; 2000-02-10 to current/open; source msha-controller-operator-history