# Relationship history for MSHA mine 1515806

Current hierarchy: **Perkins Ronald-Mitchell Helton → D & R Coal Company → No 1**

- 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

- **controller_controls_mine:** Jerry  Brock → No 1; 1985-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Bronco Mining Inc → No 1; 1986-10-01 to 1987-10-08; source msha-controller-operator-history
- **controller_controls_operator:** Jerry  Brock → Bronco Mining Inc; 1986-10-01 to 1987-10-08; source msha-controller-operator-history
- **operator_operates_mine:** D & R Coal Company → No 1; 1987-10-09 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Perkins Ronald-Mitchell Helton Et Al → No 1; 1987-10-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Perkins Ronald-Mitchell Helton Et Al → D & R Coal Company; 1987-10-09 to current/open; source msha-controller-operator-history