# Relationship history for MSHA mine 4702748

Current hierarchy: **Baraboo Asphalt Company Inc → W R Du Bois & Sons Inc → Spencer 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

- **controller_controls_mine:** Baraboo Asphalt Company Inc → Spencer Quarry; 1981-05-05 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** W R Du Bois & Sons Inc → Spencer Quarry; 1981-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Baraboo Asphalt Company Inc → W R Du Bois & Sons Inc; 1981-10-01 to current/open; source msha-controller-operator-history