# Relationship history for MSHA mine 1509605

Current hierarchy: **Keystone Coal Company → Lobb Coal Mining Company → Lobb No 1 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

- **operator_operates_mine:** Lobb Coal Mining Company → Lobb No 1 Surface; 1979-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Keystone Coal Company → Lobb No 1 Surface; 1979-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Keystone Coal Company → Lobb Coal Mining Company; 1979-06-01 to current/open; source msha-controller-operator-history