# Relationship history for MSHA mine 3800620

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta Aggregates → MYRTLE BEACH STONE YARD**

- 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:** Martin Marietta Materials Inc → MYRTLE BEACH STONE YARD; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Aggregates → MYRTLE BEACH STONE YARD; 1987-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Aggregates; 1987-01-01 to current/open; source msha-controller-operator-history