# Relationship history for MSHA mine 0503170

Current hierarchy: **Hoyl Alfred G → Coal Fuels Corp → Anchor Tresner Coal Unit**

- 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:** Dorchester Coal Company → Anchor Tresner Coal Unit; 1978-07-01 to 1987-02-06; source msha-controller-operator-history
- **controller_controls_mine:** Damson Oil Corp → Anchor Tresner Coal Unit; 1978-07-01 to 1987-02-06; source msha-controller-operator-history
- **controller_controls_operator:** Damson Oil Corp → Dorchester Coal Company; 1978-07-01 to 1987-02-06; source msha-controller-operator-history
- **operator_operates_mine:** American Shield Coal Company → Anchor Tresner Coal Unit; 1987-02-07 to 1991-04-22; source msha-controller-operator-history
- **controller_controls_mine:** Arabian Shield Development Company → Anchor Tresner Coal Unit; 1987-02-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Arabian Shield Development Company → American Shield Coal Company; 1987-02-07 to 1991-04-22; source msha-controller-operator-history
- **operator_operates_mine:** Coal Fuels Corp → Anchor Tresner Coal Unit; 1991-04-23 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hoyl Alfred G → Anchor Tresner Coal Unit; 1991-04-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hoyl Alfred G → Coal Fuels Corp; 1991-04-23 to current/open; source msha-controller-operator-history