# Relationship history for MSHA mine 2602603

Current hierarchy: **National Oilwell Varco Inc → National Oilwell Varco, LP → Big Ledge Mine**

- 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:** Spirit Minerals LP → Big Ledge Mine; 2006-08-01 to 2009-07-12; source msha-controller-operator-history
- **controller_controls_mine:** Spirit Minerals Management LLC et al → Big Ledge Mine; 2006-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Spirit Minerals Management LLC et al → Spirit Minerals LP; 2006-08-01 to 2009-07-12; source msha-controller-operator-history
- **operator_operates_mine:** National Oilwell Varco, LP → Big Ledge Mine; 2009-07-13 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** National Oilwell Varco Inc → Big Ledge Mine; 2009-07-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** National Oilwell Varco Inc → National Oilwell Varco, LP; 2009-07-13 to current/open; source msha-controller-operator-history