# Relationship history for MSHA mine 4503303

Current hierarchy: **William C  Westergreen; Rodney W  Lofdahl → A L R T Corporation → A L R T Portable Crusher**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** A.L.R.T. Corp → A L R T Portable Crusher; 1993-08-01 to 2008-03-24; source msha-controller-operator-history
- **controller_controls_mine:** Jerry  Hammer → A L R T Portable Crusher; 1993-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Jerry  Hammer → A.L.R.T. Corp; 1993-08-01 to 2008-03-24; source msha-controller-operator-history
- **operator_operates_mine:** A L R T Corporation → A L R T Portable Crusher; 2008-03-25 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rodney W  Lofdahl  et al → A L R T Portable Crusher; 2008-03-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rodney W  Lofdahl  et al → A L R T Corporation; 2008-03-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William C  Westergreen  et al → A L R T Corporation; 2008-03-25 to current/open; source msha-controller-operator-history