# Relationship history for MSHA mine 4607681

Current hierarchy: **Roberts Derrick → D V R Mining Inc → Portal B**

- 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:** R S & R Mining Inc → Portal B; 1989-03-01 to 1991-09-12; source msha-controller-operator-history
- **controller_controls_mine:** Herbert D  Roberts → Portal B; 1989-03-01 to 1991-09-12; source msha-controller-operator-history
- **controller_controls_operator:** Herbert D  Roberts → R S & R Mining Inc; 1989-03-01 to 1991-09-12; source msha-controller-operator-history
- **controller_controls_mine:** Roberts Derrick → Portal B; 1991-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** D V R Mining Inc → Portal B; 1991-09-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Roberts Derrick → D V R Mining Inc; 1991-09-13 to current/open; source msha-controller-operator-history