# Relationship history for MSHA mine 3303283

Current hierarchy: **Rybski Vernon A → Mid-Ohio Mining Company → Darr Strip Mine**

- 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:** John N Strawser & Sons Inc → Darr Strip Mine; 1975-02-06 to 1975-04-21; source msha-controller-operator-history
- **controller_controls_mine:** Strawser John N → Darr Strip Mine; 1975-02-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Strawser John N → John N Strawser & Sons Inc; 1975-02-06 to 1975-04-21; source msha-controller-operator-history
- **operator_operates_mine:** Mid-Ohio Mining Company → Darr Strip Mine; 1975-04-22 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rybski Vernon A → Darr Strip Mine; 1975-04-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rybski Vernon A → Mid-Ohio Mining Company; 1975-04-22 to current/open; source msha-controller-operator-history