# Relationship history for MSHA mine 3600924

Current hierarchy: **Rochester & Pittsburgh Coal Company → Florence Mining Company → Florence No 1 - Blacklick Portal**

- 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:** Florence Mining Company → Florence No 1 - Blacklick Portal; 1950-01-01 to 1984-09-30; source msha-controller-operator-history
- **controller_controls_mine:** NACCO Industries Inc → Florence No 1 - Blacklick Portal; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** NACCO Industries Inc → Florence Mining Company; 1950-01-01 to 1984-09-30; source msha-controller-operator-history
- **operator_operates_mine:** Florence Mining Company → Florence No 1 - Blacklick Portal; 1984-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rochester & Pittsburgh Coal Company → Florence No 1 - Blacklick Portal; 1984-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rochester & Pittsburgh Coal Company → Florence Mining Company; 1984-10-01 to current/open; source msha-controller-operator-history