# Relationship history for MSHA mine 3606206

Current hierarchy: **Standard Slag Company → Duquesne Slag Products Company → Duquesne Strip**

- 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:** Duquesne Slag Products Company → Duquesne Strip; 1976-02-10 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Standard Slag Company → Duquesne Strip; 1976-02-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Standard Slag Company → Duquesne Slag Products Company; 1976-02-10 to current/open; source msha-controller-operator-history