# Relationship history for MSHA mine 0504073

Current hierarchy: **Thelma B  Starner → Delta Sand & Gravel Company → Delta Portable Crushing Plant #1**

- 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:** Thelma B  Starner → Delta Portable Crushing Plant #1; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Delta Sand & Gravel Company → Delta Portable Crushing Plant #1; 1985-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thelma B  Starner → Delta Sand & Gravel Company; 1985-07-01 to current/open; source msha-controller-operator-history