# Relationship history for MSHA mine 3901607

Current hierarchy: **Robert Ray  Brewer → Rock Bottom Industries, Inc. → Portable Plant #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

- **operator_operates_mine:** Rock Bottom Industries, Inc. → Portable Plant #1; 2014-05-13 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Robert Ray  Brewer → Portable Plant #1; 2014-05-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert Ray  Brewer → Rock Bottom Industries, Inc.; 2014-05-13 to current/open; source msha-controller-operator-history