# Relationship history for MSHA mine 1507746

Current hierarchy: **Ballard Tom → Tom Ballard Co Inc → No 2 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Ballard Tom → No 2 Surface; 1974-05-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Tom Ballard Co Inc → No 2 Surface; 1974-11-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ballard Tom → Tom Ballard Co Inc; 1974-11-21 to current/open; source msha-controller-operator-history