# Relationship history for MSHA mine 1901019

Current hierarchy: **Dudley R  Billings → D. R. Billings, 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

- **operator_operates_mine:** D. R. Billings, Inc. → Portable Crusher; 1989-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dudley R  Billings → Portable Crusher; 1989-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dudley R  Billings → D. R. Billings, Inc.; 1989-10-01 to current/open; source msha-controller-operator-history