# Relationship history for MSHA mine 1900957

Current hierarchy: **Kurt F  Carlson → Roma Stone Corp → Westford 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:** Roma Stone Corp → Westford Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kurt F  Carlson → Westford Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kurt F  Carlson → Roma Stone Corp; 1950-01-01 to current/open; source msha-controller-operator-history