# Relationship history for MSHA mine 3200751

Current hierarchy: **Art  Mariner → Mariner Sand & Gravel Inc → PORTABLE #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:** Mariner Sand & Gravel Inc → PORTABLE #1; 1997-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Art  Mariner et al → PORTABLE #1; 1997-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Art  Mariner et al → Mariner Sand & Gravel Inc; 1997-07-01 to current/open; source msha-controller-operator-history