# Relationship history for MSHA mine 3600212

Current hierarchy: **CRH PLC → Pennsy Supply Inc → Silver Springs Quarry**

- 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:** Pennsy Supply Inc → Silver Springs Quarry; 1950-01-01 to 1993-07-20; source msha-controller-operator-history
- **controller_controls_mine:** Barbara M  Mumma → Silver Springs Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Barbara M  Mumma → Pennsy Supply Inc; 1950-01-01 to 1993-07-20; source msha-controller-operator-history
- **operator_operates_mine:** Pennsy Supply Inc → Silver Springs Quarry; 1993-07-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Silver Springs Quarry; 1993-07-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Pennsy Supply Inc; 1993-07-21 to current/open; source msha-controller-operator-history