# Relationship history for MSHA mine 3607089

Current hierarchy: **Dobkin I Todd → Allied Block Chemical Company → Therm-O-Rock**

- 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:** Allied Block Chemical Company → Therm-O-Rock; 1981-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dobkin I Todd → Therm-O-Rock; 1981-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dobkin I Todd → Allied Block Chemical Company; 1981-01-01 to current/open; source msha-controller-operator-history