# Relationship history for MSHA mine 3500014

Current hierarchy: **Gary T  Baker → Baker Rock Resources → Koehler Quarry**

- 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:** Gary T  Baker → Koehler Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** L H Cobb-Crushed Rock → Koehler Quarry; 1950-01-01 to 1984-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Cobb Lyle H → Koehler Quarry; 1950-01-01 to 1984-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Cobb Lyle H → L H Cobb-Crushed Rock; 1950-01-01 to 1984-12-31; source msha-controller-operator-history
- **operator_operates_mine:** Cobb Rock Inc → Koehler Quarry; 1985-01-01 to 1986-02-07; source msha-controller-operator-history
- **controller_controls_mine:** Roadway Constructors Corp → Koehler Quarry; 1985-01-01 to 1986-02-07; source msha-controller-operator-history
- **controller_controls_operator:** Roadway Constructors Corp → Cobb Rock Inc; 1985-01-01 to 1986-02-07; source msha-controller-operator-history
- **operator_operates_mine:** Cobb Rock Inc → Koehler Quarry; 1986-02-08 to 1987-06-25; source msha-controller-operator-history
- **controller_controls_mine:** Riedel International Inc → Koehler Quarry; 1986-02-08 to 1987-06-25; source msha-controller-operator-history
- **controller_controls_operator:** Riedel International Inc → Cobb Rock Inc; 1986-02-08 to 1987-06-25; source msha-controller-operator-history
- **operator_operates_mine:** Cobb Rock Inc → Koehler Quarry; 1987-06-26 to 1987-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Lone Star Industries Inc → Koehler Quarry; 1987-06-26 to 1987-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Lone Star Industries Inc → Cobb Rock Inc; 1987-06-26 to 1987-12-31; source msha-controller-operator-history
- **operator_operates_mine:** Northwest Aggregates → Koehler Quarry; 1988-01-01 to 2009-01-12; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Koehler Quarry; 1988-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Northwest Aggregates; 1988-01-01 to 2009-01-12; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Koehler Quarry; 1990-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Company → Koehler Quarry; 2009-01-13 to 2010-04-05; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → CalPortland Company; 2009-01-13 to 2010-04-05; source msha-controller-operator-history
- **operator_operates_mine:** Baker Rock Resources → Koehler Quarry; 2010-04-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gary T  Baker → Baker Rock Resources; 2010-04-06 to current/open; source msha-controller-operator-history