# Relationship history for MSHA mine 1507938

Current hierarchy: **Keither  Blackburn; Jack  Roberts → Billy Branch Coal Company → No 1 Surface 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:** Billy Branch Coal Company → No 1 Surface Mine; 1974-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Jack  Roberts et al → No 1 Surface Mine; 1974-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Jack  Roberts et al → Billy Branch Coal Company; 1974-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Keither  Blackburn et al → Billy Branch Coal Company; 1974-12-01 to current/open; source msha-controller-operator-history