# Relationship history for MSHA mine 3606663

Current hierarchy: **Kerametal Company Ltd → American Carbon & Metals Corp → Donora Dock**

- 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:** Campbell Coal Company Inc → Donora Dock; 1978-05-01 to 1981-12-21; source msha-controller-operator-history
- **controller_controls_mine:** Campbell George R → Donora Dock; 1978-05-01 to 1981-12-21; source msha-controller-operator-history
- **controller_controls_operator:** Campbell George R → Campbell Coal Company Inc; 1978-05-01 to 1981-12-21; source msha-controller-operator-history
- **controller_controls_mine:** Hooversville Coal Company Et Al → Donora Dock; 1978-08-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Northbrook Mining Inc → Donora Dock; 1981-12-22 to 1984-03-06; source msha-controller-operator-history
- **controller_controls_mine:** Northbrook Metals Inc → Donora Dock; 1981-12-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Northbrook Metals Inc → Northbrook Mining Inc; 1981-12-22 to 1984-03-06; source msha-controller-operator-history
- **operator_operates_mine:** Intercarbon Coal Company → Donora Dock; 1984-03-07 to 1988-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Hooversville Coal Company Et Al → Intercarbon Coal Company; 1984-03-07 to 1988-10-31; source msha-controller-operator-history
- **controller_controls_mine:** William D  Renton et al → Donora Dock; 1987-04-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hardhat Mining Inc → Donora Dock; 1988-11-01 to 1989-05-03; source msha-controller-operator-history
- **controller_controls_operator:** William D  Renton et al → Hardhat Mining Inc; 1988-11-01 to 1989-05-03; source msha-controller-operator-history
- **controller_controls_operator:** James T  Arnone et al → Hardhat Mining Inc; 1988-11-01 to 1989-05-03; source msha-controller-operator-history
- **operator_operates_mine:** American Carbon & Metals Corp → Donora Dock; 1989-05-04 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kerametal Company Ltd → Donora Dock; 1989-05-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kerametal Company Ltd → American Carbon & Metals Corp; 1989-05-04 to current/open; source msha-controller-operator-history