# Relationship history for MSHA mine 4606035

Current hierarchy: **Dempsey William K → D K D Coal Corp → No 1 Surface**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** Petersville Sleigh Ltd Et Al → No 1 Surface; 1978-08-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Westphalia Coal Corp → No 1 Surface; 1979-10-01 to 1980-05-11; source msha-controller-operator-history
- **controller_controls_operator:** Petersville Sleigh Ltd Et Al → Westphalia Coal Corp; 1979-10-01 to 1980-05-11; source msha-controller-operator-history
- **controller_controls_mine:** Schlabach Alvin A → No 1 Surface; 1979-11-01 to 1982-03-24; source msha-controller-operator-history
- **operator_operates_mine:** Delta Energy Inc → No 1 Surface; 1980-05-12 to 1981-09-29; source msha-controller-operator-history
- **controller_controls_operator:** Schlabach Alvin A → Delta Energy Inc; 1980-05-12 to 1981-09-29; source msha-controller-operator-history
- **operator_operates_mine:** D K D Coal Corp → No 1 Surface; 1981-09-30 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dempsey William K → No 1 Surface; 1981-09-30 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dempsey William K → D K D Coal Corp; 1981-09-30 to current/open; source msha-controller-operator-history