# Relationship history for MSHA mine 4406373

Current hierarchy: **Gary  Baker → Ivy Branch Coal Company Inc → No 18 Mine**

- 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:** Coleman Hufford-Mary Ruth Et Al → No 18 Mine; 1975-09-10 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Blue Chip Coal Corp → No 18 Mine; 1987-04-01 to 1991-07-24; source msha-controller-operator-history
- **controller_controls_operator:** Coleman Hufford-Mary Ruth Et Al → Blue Chip Coal Corp; 1987-04-01 to 1991-07-24; source msha-controller-operator-history
- **controller_controls_mine:** Gary  Baker → No 18 Mine; 1990-05-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Ivy Branch Coal Company Inc → No 18 Mine; 1991-07-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gary  Baker → Ivy Branch Coal Company Inc; 1991-07-25 to current/open; source msha-controller-operator-history