# Relationship history for MSHA mine 5001505

Current hierarchy: **Robert B  Fisher → Fisher'S Gravel → Fisher'S Portable**

- 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:** Fisher'S Gravel → Fisher'S Portable; 1986-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Robert B  Fisher → Fisher'S Portable; 1986-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert B  Fisher → Fisher'S Gravel; 1986-06-01 to current/open; source msha-controller-operator-history