# Relationship history for MSHA mine 1509879

Current hierarchy: **Bowling Charles D → Crystal Coal Company → No 1 Mine (D)**

- 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:** Michael  Derry et al → No 1 Mine (D); 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Bowling Charles D Et Al → No 1 Mine (D); 1973-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Bentley & Derry Coal Company Inc → No 1 Mine (D); 1976-08-11 to 1979-05-21; source msha-controller-operator-history
- **controller_controls_operator:** Michael  Derry et al → Bentley & Derry Coal Company Inc; 1976-08-11 to 1979-05-21; source msha-controller-operator-history
- **controller_controls_operator:** James E Derry et al → Bentley & Derry Coal Company Inc; 1976-08-11 to 1979-05-21; source msha-controller-operator-history
- **controller_controls_mine:** Smallwood Lenard → No 1 Mine (D); 1978-02-28 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Lenard Mining Company → No 1 Mine (D); 1979-05-22 to 1979-08-08; source msha-controller-operator-history
- **controller_controls_operator:** Smallwood Lenard → Lenard Mining Company; 1979-05-22 to 1979-08-08; source msha-controller-operator-history
- **operator_operates_mine:** Crystal Coal Company → No 1 Mine (D); 1979-08-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bowling Charles D Et Al → Crystal Coal Company; 1979-08-09 to current/open; source msha-controller-operator-history