# Relationship history for MSHA mine 3503301

Current hierarchy: **Fred  Sohn → Lone Rock Timber Company → Portable Drill Crew #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:** Fred  Sohn → Portable Drill Crew #1; 1987-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Lone Rock Timber Company → Portable Drill Crew #1; 1988-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Fred  Sohn → Lone Rock Timber Company; 1988-01-01 to current/open; source msha-controller-operator-history