# Relationship history for MSHA mine 3605487

Current hierarchy: **Penn Erection & Rigging → Penn Terra Ltd → Hilty 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Penn Terra Ltd → Hilty Strip; 1975-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Penn Erection & Rigging → Hilty Strip; 1975-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Penn Erection & Rigging → Penn Terra Ltd; 1975-02-01 to current/open; source msha-controller-operator-history