# Relationship history for MSHA mine 1506391

Current hierarchy: **Basic American Industries → Mary Helen Coal Company Inc → No 2 Tipple**

- 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:** Hawkeye Elkhorn Coal Company Inc → No 2 Tipple; 1950-01-01 to 1974-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Potter Hobert E → No 2 Tipple; 1950-01-01 to 1974-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Potter Hobert E → Hawkeye Elkhorn Coal Company Inc; 1950-01-01 to 1974-12-31; source msha-controller-operator-history
- **operator_operates_mine:** Hawkeye Elkhorn Coal Company Inc → No 2 Tipple; 1975-01-01 to 1978-11-27; source msha-controller-operator-history
- **controller_controls_mine:** Schwab Charles F → No 2 Tipple; 1975-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Schwab Charles F → Hawkeye Elkhorn Coal Company Inc; 1975-01-01 to 1978-11-27; source msha-controller-operator-history
- **controller_controls_mine:** Basic American Industries → No 2 Tipple; 1976-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Falcon Seaboard Inc → No 2 Tipple; 1978-09-01 to 1979-01-31; source msha-controller-operator-history
- **operator_operates_mine:** Hawkeye Elkhorn Coal Company Inc → No 2 Tipple; 1978-11-28 to 1979-01-31; source msha-controller-operator-history
- **controller_controls_operator:** Falcon Seaboard Inc → Hawkeye Elkhorn Coal Company Inc; 1978-11-28 to 1979-01-31; source msha-controller-operator-history
- **operator_operates_mine:** Hawkeye Services Corp → No 2 Tipple; 1979-02-01 to 1984-07-17; source msha-controller-operator-history
- **controller_controls_mine:** Diamond Shamrock Corp → No 2 Tipple; 1979-02-01 to 1987-05-17; source msha-controller-operator-history
- **controller_controls_operator:** Diamond Shamrock Corp → Hawkeye Services Corp; 1979-02-01 to 1984-07-17; source msha-controller-operator-history
- **operator_operates_mine:** Coal Bank Inc → No 2 Tipple; 1984-07-18 to 1985-03-18; source msha-controller-operator-history
- **controller_controls_mine:** Hart Homer O → No 2 Tipple; 1984-07-18 to 1985-03-18; source msha-controller-operator-history
- **controller_controls_operator:** Hart Homer O → Coal Bank Inc; 1984-07-18 to 1985-03-18; source msha-controller-operator-history
- **operator_operates_mine:** Hawkeye Services Corp → No 2 Tipple; 1985-03-19 to 1985-10-20; source msha-controller-operator-history
- **controller_controls_operator:** Diamond Shamrock Corp → Hawkeye Services Corp; 1985-03-19 to 1985-10-20; source msha-controller-operator-history
- **operator_operates_mine:** Mary Helen Coal Company Inc → No 2 Tipple; 1985-10-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Basic American Industries → Mary Helen Coal Company Inc; 1985-10-21 to current/open; source msha-controller-operator-history