# Relationship history for MSHA mine 2102704

Current hierarchy: **Martin Marietta Materials Inc → Barton Sand & Gravel → 86-222 Portable 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Commercial Asphalt Company → 86-222 Portable Mill; 1979-01-01 to 1983-02-28; source msha-controller-operator-history
- **controller_controls_mine:** Eugene  Barton → 86-222 Portable Mill; 1979-01-01 to 1983-02-28; source msha-controller-operator-history
- **controller_controls_operator:** Eugene  Barton → Commercial Asphalt Company; 1979-01-01 to 1983-02-28; source msha-controller-operator-history
- **operator_operates_mine:** Barton Sand & Gravel → 86-222 Portable Mill; 1983-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Tiller Corp → 86-222 Portable Mill; 1983-03-01 to 2021-05-03; source msha-controller-operator-history
- **controller_controls_operator:** Tiller Corp → Barton Sand & Gravel; 1983-03-01 to 2021-05-03; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → 86-222 Portable Mill; 2021-05-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Barton Sand & Gravel; 2021-05-04 to current/open; source msha-controller-operator-history