# Relationship history for MSHA mine 3503520

Current hierarchy: **MDU Resources Group Inc → Hap Taylor & Sons Inc → Portable Crusher**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** MDU Resources Group Inc → Portable Crusher; 1999-03-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hap Taylor & Sons Inc → Portable Crusher; 2001-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → Hap Taylor & Sons Inc; 2001-02-01 to current/open; source msha-controller-operator-history