# Relationship history for MSHA mine 2103707

Current hierarchy: **Mark T  Thorson → Mark Sand & Gravel Co. → Mark Sand & Gravel Co. 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:** Mark T  Thorson → Mark Sand & Gravel Co. Quarry; 1997-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Mark Sand & Gravel Co. → Mark Sand & Gravel Co. Quarry; 2010-07-30 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mark T  Thorson → Mark Sand & Gravel Co.; 2010-07-30 to current/open; source msha-controller-operator-history