# Relationship history for MSHA mine 1509831

Current hierarchy: **Mc David J W → Union Boiler Company → Union Boiler No 4 Surface**

- 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:** Mc David J W → Union Boiler No 4 Surface; 1975-09-10 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Union Boiler Company → Union Boiler No 4 Surface; 1976-05-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mc David J W → Union Boiler Company; 1976-05-18 to current/open; source msha-controller-operator-history