# Relationship history for MSHA mine 1700765

Current hierarchy: **Benjamin C Grover → A H Grover Inc → Extec Plant**

- 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:** Alwin H  Grover → Extec Plant; 1988-03-01 to 2024-10-31; source msha-controller-operator-history
- **operator_operates_mine:** A H Grover Inc → Extec Plant; 2002-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Alwin H  Grover → A H Grover Inc; 2002-11-01 to 2024-10-31; source msha-controller-operator-history
- **controller_controls_mine:** Benjamin C Grover → Extec Plant; 2024-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Benjamin C Grover → A H Grover Inc; 2024-11-01 to current/open; source msha-controller-operator-history