# Relationship history for MSHA mine 3400939

Current hierarchy: **Hefner Jess & Don → Hefner & Son Coal Company → Davis No 1 Strip**

- 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:** Hefner & Son Coal Company → Davis No 1 Strip; 1976-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hefner Jess & Don → Davis No 1 Strip; 1976-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hefner Jess & Don → Hefner & Son Coal Company; 1976-01-01 to current/open; source msha-controller-operator-history