# Relationship history for MSHA mine 4502620

Current hierarchy: **Johnson L M → L M Johnson Inc → Black Rock Quarry - Index #51**

- 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:** Johnson L M → Black Rock Quarry - Index #51; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** L M Johnson Inc → Black Rock Quarry - Index #51; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Johnson L M → L M Johnson Inc; 1979-01-01 to current/open; source msha-controller-operator-history