# Relationship history for MSHA mine 1700542

Current hierarchy: **Bridge John C → Bridgecorp → Portable Screen #1635**

- 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

- **controller_controls_mine:** Bridge John C → Portable Screen #1635; 1980-04-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Bridgecorp → Portable Screen #1635; 1981-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bridge John C → Bridgecorp; 1981-04-01 to current/open; source msha-controller-operator-history