# Relationship history for MSHA mine 1701152

Current hierarchy: **Heather A Gallant; Zachary H Stevenson → C.H. Stevenson Inc. → Portable Screen**

- 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:** Heather A Gallant et al → Portable Screen; 2025-01-06 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** C.H. Stevenson Inc. → Portable Screen; 2025-05-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heather A Gallant et al → C.H. Stevenson Inc.; 2025-05-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Zachary H Stevenson et al → C.H. Stevenson Inc.; 2025-05-21 to current/open; source msha-controller-operator-history