# Relationship history for MSHA mine 1100881

Current hierarchy: **Avitar Industries Inc → Tammsco Inc → Birk No 2 Pit**

- 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:** Tammsco Inc → Birk No 2 Pit; 1950-01-01 to 1984-03-14; source msha-controller-operator-history
- **controller_controls_mine:** John  Norton → Birk No 2 Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** John  Norton → Tammsco Inc; 1950-01-01 to 1984-03-14; source msha-controller-operator-history
- **operator_operates_mine:** Tammsco Inc → Birk No 2 Pit; 1984-03-15 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Avitar Industries Inc → Birk No 2 Pit; 1984-03-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Avitar Industries Inc → Tammsco Inc; 1984-03-15 to current/open; source msha-controller-operator-history