# Relationship history for MSHA mine 4702150

Current hierarchy: **Baraboo Asphalt Company Inc → Baraboo Asphalt Company Inc → Portable Unit No 1**

- 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:** W R Du Bois & Son Inc → Portable Unit No 1; 1950-01-01 to 1981-05-04; source msha-controller-operator-history
- **controller_controls_mine:** Du Bois Lloyd → Portable Unit No 1; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Du Bois Lloyd → W R Du Bois & Son Inc; 1950-01-01 to 1981-05-04; source msha-controller-operator-history
- **operator_operates_mine:** Baraboo Asphalt Company Inc → Portable Unit No 1; 1981-05-05 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Baraboo Asphalt Company Inc → Portable Unit No 1; 1981-05-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Baraboo Asphalt Company Inc → Baraboo Asphalt Company Inc; 1981-05-05 to current/open; source msha-controller-operator-history