# Relationship history for MSHA mine 4502994

Current hierarchy: **Pamp  Maiers → North Central Construction → Portable Crusher #1**

- 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:** N A Degerstrom → Portable Crusher #1; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** N A Degerstrom Inc → Portable Crusher #1; 1983-03-01 to 2003-06-26; source msha-controller-operator-history
- **controller_controls_operator:** N A Degerstrom → N A Degerstrom Inc; 1983-03-01 to 2003-06-26; source msha-controller-operator-history
- **controller_controls_mine:** Pamp  Maiers → Portable Crusher #1; 1984-09-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** North Central Construction → Portable Crusher #1; 2003-06-27 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Pamp  Maiers → North Central Construction; 2003-06-27 to current/open; source msha-controller-operator-history