# Relationship history for MSHA mine 3605681

Current hierarchy: **Hoffman David & Glenn → H B & H Coal Company → Four Vein Drift**

- 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:** H B & H Coal Company → Four Vein Drift; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hoffman David & Glenn Et Al → Four Vein Drift; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hoffman David & Glenn Et Al → H B & H Coal Company; 1950-01-01 to current/open; source msha-controller-operator-history