# Relationship history for MSHA mine 1900503

Current hierarchy: **Edwin C  Williams → Williams Stone Co. Inc → Berkshire Quarry**

- 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:** Williams Stone Co. Inc → Berkshire Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Edwin C  Williams → Berkshire Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Edwin C  Williams → Williams Stone Co. Inc; 1950-01-01 to current/open; source msha-controller-operator-history