# Relationship history for MSHA mine 0502671

Current hierarchy: **Dravo Corp → Dravo Corp → Letty Jones 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:** Cotter Corp → Letty Jones Mine; 1950-01-01 to 1978-07-31; source msha-controller-operator-history
- **controller_controls_mine:** Commonwealth Edison Company → Letty Jones Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Commonwealth Edison Company → Cotter Corp; 1950-01-01 to 1978-07-31; source msha-controller-operator-history
- **controller_controls_mine:** Tripp W D Mining Company → Letty Jones Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** W D Tripp Mining Company → Letty Jones Mine; 1978-08-01 to 1979-07-22; source msha-controller-operator-history
- **controller_controls_operator:** Tripp W D Mining Company → W D Tripp Mining Company; 1978-08-01 to 1979-07-22; source msha-controller-operator-history
- **operator_operates_mine:** Dravo Corp → Letty Jones Mine; 1979-07-23 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dravo Corp → Letty Jones Mine; 1979-07-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dravo Corp → Dravo Corp; 1979-07-23 to current/open; source msha-controller-operator-history