# Relationship history for MSHA mine 3503262

Current hierarchy: **Willingham Ken → Calkins Sand & Gravel → Doyle Mine**

- 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

- **operator_operates_mine:** Calkins Sand & Gravel → Doyle Mine; 1986-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Willingham Ken → Doyle Mine; 1986-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Willingham Ken → Calkins Sand & Gravel; 1986-06-01 to current/open; source msha-controller-operator-history