# Relationship history for MSHA mine 1200694

Current hierarchy: **Bill  Schmaltz → Laughery Gravel Company → Laughery Gravel Company**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** Dravo Corp → Laughery Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Laughery Gravel Company → Laughery Gravel Company; 1950-01-01 to 1978-06-13; source msha-controller-operator-history
- **controller_controls_mine:** Bill  Schmaltz → Laughery Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bill  Schmaltz → Laughery Gravel Company; 1950-01-01 to 1978-06-13; source msha-controller-operator-history
- **operator_operates_mine:** Dravo Natural Resources Company Inc → Laughery Gravel Company; 1978-06-14 to 1985-07-31; source msha-controller-operator-history
- **controller_controls_operator:** Dravo Corp → Dravo Natural Resources Company Inc; 1978-06-14 to 1985-07-31; source msha-controller-operator-history
- **operator_operates_mine:** Laughery Gravel Company → Laughery Gravel Company; 1985-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bill  Schmaltz → Laughery Gravel Company; 1985-08-01 to current/open; source msha-controller-operator-history