# Relationship history for MSHA mine 1516421

Current hierarchy: **Ward Darrell E-Mark → Unity Partnership → Sharp Property**

- 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:** Unity Partnership → Sharp Property; 1988-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ward Darrell E-Mark Et Al → Sharp Property; 1988-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ward Darrell E-Mark Et Al → Unity Partnership; 1988-07-01 to current/open; source msha-controller-operator-history