# Relationship history for MSHA mine 3602821

Current hierarchy: **Vincent  Kassa → Silverbrook Anthracite Inc → Twin Slope**

- 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:** Z & F Coal Co → Twin Slope; 1950-01-01 to 1974-10-22; source msha-controller-operator-history
- **controller_controls_mine:** Z & F Coal Company → Twin Slope; 1950-01-01 to 1974-10-22; source msha-controller-operator-history
- **controller_controls_operator:** Z & F Coal Company → Z & F Coal Co; 1950-01-01 to 1974-10-22; source msha-controller-operator-history
- **controller_controls_mine:** Vincent  Kassa → Twin Slope; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Silverbrook Anthracite Inc → Twin Slope; 1974-10-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Vincent  Kassa → Silverbrook Anthracite Inc; 1974-10-23 to current/open; source msha-controller-operator-history