# Relationship history for MSHA mine 2501028

Current hierarchy: **Thomas E  Frick → Frick Sand & Gravel Inc → Pit #4**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Thomas E  Frick → Pit #4; 1984-06-13 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Frontier County → Pit #4; 1985-09-01 to 1991-06-17; source msha-controller-operator-history
- **controller_controls_mine:** Frontier County-Ne → Pit #4; 1985-09-01 to 1991-06-17; source msha-controller-operator-history
- **controller_controls_operator:** Frontier County-Ne → Frontier County; 1985-09-01 to 1991-06-17; source msha-controller-operator-history
- **operator_operates_mine:** Frick Sand & Gravel Inc → Pit #4; 1991-06-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thomas E  Frick → Frick Sand & Gravel Inc; 1991-06-18 to current/open; source msha-controller-operator-history