# Relationship history for MSHA mine 2003457

Current hierarchy: **Mona  Albrecht → Albrecht Sand & Gravel Co. → Dry Screener**

- 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:** Robert G  Albrecht → Dry Screener; 1950-01-01 to 2021-01-15; source msha-controller-operator-history
- **operator_operates_mine:** Albrecht Sand & Gravel Co. → Dry Screener; 2012-04-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert G  Albrecht → Albrecht Sand & Gravel Co.; 2012-04-05 to 2021-01-15; source msha-controller-operator-history
- **controller_controls_mine:** Mona  Albrecht → Dry Screener; 2021-01-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mona  Albrecht → Albrecht Sand & Gravel Co.; 2021-01-16 to current/open; source msha-controller-operator-history