# Relationship history for MSHA mine 1700969

Current hierarchy: **Aubrey G  Engstrom; Gary S  Engstrom → ABS Construction Inc. → Portable Track Screen**

- 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:** Gary S  Engstrom  et al → Portable Track Screen; 2007-04-26 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** ABS Construction Inc. → Portable Track Screen; 2015-10-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gary S  Engstrom  et al → ABS Construction Inc.; 2015-10-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Aubrey G  Engstrom  et al → ABS Construction Inc.; 2015-10-21 to current/open; source msha-controller-operator-history