# Relationship history for MSHA mine 1510968

Current hierarchy: **Blair David → Sand Bar Mining Inc → No 2 Surface 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Seminole Coal Company Inc → No 2 Surface Mine; 1977-11-01 to 1979-01-21; source msha-controller-operator-history
- **controller_controls_mine:** Johnson Richard → No 2 Surface Mine; 1977-11-01 to 1979-01-21; source msha-controller-operator-history
- **controller_controls_operator:** Johnson Richard → Seminole Coal Company Inc; 1977-11-01 to 1979-01-21; source msha-controller-operator-history
- **controller_controls_mine:** Blair David → No 2 Surface Mine; 1978-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sand Bar Mining Inc → No 2 Surface Mine; 1979-01-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Blair David → Sand Bar Mining Inc; 1979-01-22 to current/open; source msha-controller-operator-history