# Relationship history for MSHA mine 1800820

Current hierarchy: **Spencer J Svonavec → Simkol Corp. → Midland Mine**

- 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

- **controller_controls_mine:** Donald  Simpson → Midland Mine; 2013-01-11 to 2022-03-28; source msha-controller-operator-history
- **controller_controls_mine:** Spencer J Svonavec → Midland Mine; 2022-03-29 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Simkol Corp. → Midland Mine; 2023-12-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Spencer J Svonavec → Simkol Corp.; 2023-12-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Donald  Simpson → Simkol Corp.; 2023-12-04 to 2022-03-28; source msha-controller-operator-history