# Relationship history for MSHA mine 3607018

Current hierarchy: **Derck Robert L Sr & Jr → A L Coal Company → Robert L Derck 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

- **operator_operates_mine:** T A G Coal Company → Robert L Derck Mine; 1980-08-01 to 1984-01-18; source msha-controller-operator-history
- **controller_controls_mine:** Grego Stanley F Et Al → Robert L Derck Mine; 1980-08-01 to 1984-01-18; source msha-controller-operator-history
- **controller_controls_operator:** Grego Stanley F Et Al → T A G Coal Company; 1980-08-01 to 1984-01-18; source msha-controller-operator-history
- **operator_operates_mine:** T A G Coal Company → Robert L Derck Mine; 1984-01-19 to 1990-04-18; source msha-controller-operator-history
- **controller_controls_mine:** Troxell C Wayne Jr → Robert L Derck Mine; 1984-01-19 to 1990-04-18; source msha-controller-operator-history
- **controller_controls_operator:** Troxell C Wayne Jr → T A G Coal Company; 1984-01-19 to 1990-04-18; source msha-controller-operator-history
- **operator_operates_mine:** Sheldon Derck → Robert L Derck Mine; 1990-04-19 to 1998-07-12; source msha-controller-operator-history
- **controller_controls_mine:** Sheldon  Derck → Robert L Derck Mine; 1990-04-19 to 1998-07-12; source msha-controller-operator-history
- **controller_controls_operator:** Sheldon  Derck → Sheldon Derck; 1990-04-19 to 1998-07-12; source msha-controller-operator-history
- **operator_operates_mine:** A L Coal Company → Robert L Derck Mine; 1998-07-13 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Derck Robert L Sr & Jr → Robert L Derck Mine; 1998-07-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Derck Robert L Sr & Jr → A L Coal Company; 1998-07-13 to current/open; source msha-controller-operator-history