# Relationship history for MSHA mine 0404423

Current hierarchy: **James M  Syar → Syar Industries Inc → Potrero Hills 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** James M  Syar et al → Potrero Hills Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Potrero Sand & Gravel Inc → Potrero Hills Quarry; 1980-01-01 to 1985-10-06; source msha-controller-operator-history
- **controller_controls_mine:** Burkdoll F B → Potrero Hills Quarry; 1980-01-01 to 1985-10-06; source msha-controller-operator-history
- **controller_controls_operator:** Burkdoll F B → Potrero Sand & Gravel Inc; 1980-01-01 to 1985-10-06; source msha-controller-operator-history
- **operator_operates_mine:** Amos & Andrews Inc → Potrero Hills Quarry; 1985-10-07 to 1989-06-25; source msha-controller-operator-history
- **controller_controls_mine:** Andrews Frank J Et Al → Potrero Hills Quarry; 1985-10-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Andrews Frank J Et Al → Amos & Andrews Inc; 1985-10-07 to 1989-06-25; source msha-controller-operator-history
- **operator_operates_mine:** Syar Industries Inc → Potrero Hills Quarry; 1989-06-26 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** James M  Syar et al → Syar Industries Inc; 1989-06-26 to current/open; source msha-controller-operator-history