# Relationship history for MSHA mine 3401505

Current hierarchy: **Smith Richard L → S & S Sand-Gravel → S & S Sand**

- 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:** Hoffman W D → S & S Sand; 1978-03-09 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Job Construction Company Inc → S & S Sand; 1985-07-01 to 1990-02-12; source msha-controller-operator-history
- **controller_controls_operator:** Hoffman W D → Job Construction Company Inc; 1985-07-01 to 1990-02-12; source msha-controller-operator-history
- **operator_operates_mine:** S & S Sand-Gravel → S & S Sand; 1990-02-13 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Smith Richard L → S & S Sand; 1990-02-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Smith Richard L → S & S Sand-Gravel; 1990-02-13 to current/open; source msha-controller-operator-history