# Relationship history for MSHA mine 2500287

Current hierarchy: **Thomas E  Frick → Frick Readymix Inc → Brown Pit**

- 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

- **operator_operates_mine:** Mc Cook Sand & Gravel Company → Brown Pit; 1950-01-01 to 1987-03-19; source msha-controller-operator-history
- **controller_controls_mine:** Heimes Don → Brown Pit; 1950-01-01 to 1987-03-19; source msha-controller-operator-history
- **controller_controls_operator:** Heimes Don → Mc Cook Sand & Gravel Company; 1950-01-01 to 1987-03-19; source msha-controller-operator-history
- **operator_operates_mine:** Frick Readymix Inc → Brown Pit; 1987-03-20 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Thomas E  Frick → Brown Pit; 1987-03-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thomas E  Frick → Frick Readymix Inc; 1987-03-20 to current/open; source msha-controller-operator-history