# Relationship history for MSHA mine 0800721

Current hierarchy: **Michael W  Roberts → Roberts Sand Company LLLP → Cumbaa**

- 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:** Blountstown Sand Company → Cumbaa; 1950-01-01 to 1987-03-01; source msha-controller-operator-history
- **controller_controls_mine:** L R  Overholt  et al → Cumbaa; 1950-01-01 to 1987-03-01; source msha-controller-operator-history
- **controller_controls_operator:** L R  Overholt  et al → Blountstown Sand Company; 1950-01-01 to 1987-03-01; source msha-controller-operator-history
- **controller_controls_mine:** Michael W  Roberts → Cumbaa; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Roberts Sand Company LLLP → Cumbaa; 1987-03-02 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Michael W  Roberts → Roberts Sand Company LLLP; 1987-03-02 to current/open; source msha-controller-operator-history