# Relationship history for MSHA mine 0405237

Current hierarchy: **Karen R  Blue; Maureen E  Zills → Cal-Grade Inc → Crushing Screening**

- 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:** Wayne T  Zills → Crushing Screening; 1990-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Masters Const-Div/Farmers Land Leveling Inc → Crushing Screening; 1994-03-01 to 1999-07-11; source msha-controller-operator-history
- **controller_controls_operator:** Wayne T  Zills → Masters Const-Div/Farmers Land Leveling Inc; 1994-03-01 to 1999-07-11; source msha-controller-operator-history
- **operator_operates_mine:** Cal-Grade Inc → Crushing Screening; 1999-07-12 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Maureen E  Zills  et al → Crushing Screening; 1999-07-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Maureen E  Zills  et al → Cal-Grade Inc; 1999-07-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Karen R  Blue  et al → Cal-Grade Inc; 1999-07-12 to current/open; source msha-controller-operator-history