# Relationship history for MSHA mine 3605939

Current hierarchy: **Rantovich Donald → Mt Thor Minerals Inc → Margaret Strip 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:** J B R Inc → Margaret Strip Mine; 1950-01-01 to 1976-08-31; source msha-controller-operator-history
- **controller_controls_mine:** Walshak Robert → Margaret Strip Mine; 1950-01-01 to 1976-08-31; source msha-controller-operator-history
- **controller_controls_operator:** Walshak Robert → J B R Inc; 1950-01-01 to 1976-08-31; source msha-controller-operator-history
- **operator_operates_mine:** Leonard Sasso Company → Margaret Strip Mine; 1976-09-01 to 1977-08-28; source msha-controller-operator-history
- **controller_controls_mine:** Sasso Leonard Company → Margaret Strip Mine; 1976-09-01 to 1977-08-28; source msha-controller-operator-history
- **controller_controls_operator:** Sasso Leonard Company → Leonard Sasso Company; 1976-09-01 to 1977-08-28; source msha-controller-operator-history
- **operator_operates_mine:** Mt Thor Minerals Inc → Margaret Strip Mine; 1977-08-29 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rantovich Donald → Margaret Strip Mine; 1977-08-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rantovich Donald → Mt Thor Minerals Inc; 1977-08-29 to current/open; source msha-controller-operator-history