# Relationship history for MSHA mine 4800278

Current hierarchy: **Hoffbuhr Ready Mix → Hoffbuhr Ready Mix → Sand & Gravel Operations**

- 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:** Hoffbuhr Ready Mix → Sand & Gravel Operations; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hoffbuhr Ready Mix → Sand & Gravel Operations; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hoffbuhr Ready Mix → Hoffbuhr Ready Mix; 1950-01-01 to current/open; source msha-controller-operator-history