# Relationship history for MSHA mine 0405931

Current hierarchy: **Robar Enterprises Inc → Hi-Grade Materials Co. → HGM Nebo**

- 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:** Robar Enterprises Inc → HGM Nebo; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hi-Grade Materials Co. → HGM Nebo; 2018-11-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robar Enterprises Inc → Hi-Grade Materials Co.; 2018-11-03 to current/open; source msha-controller-operator-history