# Relationship history for MSHA mine 4503274

Current hierarchy: **Marilyn  Webb; Ron  Webb → Aphis Ready Mix → Aphis Portable Screen**

- 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:** Aphis Ready Mix → Aphis Portable Screen; 1992-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ron  Webb  et al → Aphis Portable Screen; 1992-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ron  Webb  et al → Aphis Ready Mix; 1992-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Marilyn  Webb  et al → Aphis Ready Mix; 1992-08-01 to current/open; source msha-controller-operator-history