# Relationship history for MSHA mine 0202535

Current hierarchy: **Martin Michael → Martin & Brown Inc → Arizona Rock & Sand**

- 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:** Arizona Rock & Sand Inc → Arizona Rock & Sand; 1990-10-01 to 1991-04-30; source msha-controller-operator-history
- **controller_controls_mine:** Graham Robert R → Arizona Rock & Sand; 1990-10-01 to 1991-04-30; source msha-controller-operator-history
- **controller_controls_operator:** Graham Robert R → Arizona Rock & Sand Inc; 1990-10-01 to 1991-04-30; source msha-controller-operator-history
- **operator_operates_mine:** Martin & Brown Inc → Arizona Rock & Sand; 1991-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Martin Michael → Arizona Rock & Sand; 1991-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Michael → Martin & Brown Inc; 1991-05-01 to current/open; source msha-controller-operator-history