# Relationship history for MSHA mine 4801521

Current hierarchy: **Kolar Laurence → Rock Solid Inc → ROCK SOLID 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

- **controller_controls_mine:** Salveson Robert A → ROCK SOLID PORTABLE #1; 1987-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Salveson Construction Company → ROCK SOLID PORTABLE #1; 1994-05-01 to 1995-01-23; source msha-controller-operator-history
- **controller_controls_operator:** Salveson Robert A → Salveson Construction Company; 1994-05-01 to 1995-01-23; source msha-controller-operator-history
- **operator_operates_mine:** Rock Solid Inc → ROCK SOLID PORTABLE #1; 1995-01-24 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kolar Laurence → ROCK SOLID PORTABLE #1; 1995-01-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kolar Laurence → Rock Solid Inc; 1995-01-24 to current/open; source msha-controller-operator-history