# Relationship history for MSHA mine 3607915

Current hierarchy: **Robert J  Johnson Sr → Bob Johnson Flagstone Inc → Sharer Quarry**

- 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:** Donald Johnson Flagstone → Sharer Quarry; 1987-09-01 to 1992-09-23; source msha-controller-operator-history
- **controller_controls_mine:** Donald E  Johnson → Sharer Quarry; 1987-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Donald E  Johnson → Donald Johnson Flagstone; 1987-09-01 to 1992-09-23; source msha-controller-operator-history
- **controller_controls_mine:** Robert J  Johnson Sr → Sharer Quarry; 1987-09-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Bob Johnson Flagstone Inc → Sharer Quarry; 1992-09-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert J  Johnson Sr → Bob Johnson Flagstone Inc; 1992-09-24 to current/open; source msha-controller-operator-history