# Relationship history for MSHA mine 3302911

Current hierarchy: **Zisle Don S → Shamrock Sand & Gravel Company Inc → Shamrock Pit & Mill**

- 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:** C J Bailey Sand & Gravel Company → Shamrock Pit & Mill; 1950-01-01 to 1979-04-10; source msha-controller-operator-history
- **controller_controls_mine:** Bailey C J Sand & Gravel Company → Shamrock Pit & Mill; 1950-01-01 to 1979-04-10; source msha-controller-operator-history
- **controller_controls_operator:** Bailey C J Sand & Gravel Company → C J Bailey Sand & Gravel Company; 1950-01-01 to 1979-04-10; source msha-controller-operator-history
- **operator_operates_mine:** Shamrock Sand & Gravel Company Inc → Shamrock Pit & Mill; 1979-04-11 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Zisle Don S → Shamrock Pit & Mill; 1979-04-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Zisle Don S → Shamrock Sand & Gravel Company Inc; 1979-04-11 to current/open; source msha-controller-operator-history