# Relationship history for MSHA mine 3608167

Current hierarchy: **Donton Ronald C & Richard Kroh → B K & K Coal Company → B K & K Coal Co**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** B K & K Coal Company → B K & K Coal Co; 1990-05-01 to 1994-04-17; source msha-controller-operator-history
- **controller_controls_mine:** Kroh Michael A → B K & K Coal Co; 1990-05-01 to 1994-04-17; source msha-controller-operator-history
- **controller_controls_operator:** Kroh Michael A → B K & K Coal Company; 1990-05-01 to 1994-04-17; source msha-controller-operator-history
- **operator_operates_mine:** B K & K Coal Company → B K & K Coal Co; 1994-04-18 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Donton Ronald C & Richard Kroh → B K & K Coal Co; 1994-04-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Donton Ronald C & Richard Kroh → B K & K Coal Company; 1994-04-18 to current/open; source msha-controller-operator-history