# Relationship history for MSHA mine 0504167

Current hierarchy: **Allen Robert → Frontier Construction Company → Gunnison 32 Rd 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Frontier Construction Company → Gunnison 32 Rd Quarry; 1986-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Allen Robert → Gunnison 32 Rd Quarry; 1986-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Allen Robert → Frontier Construction Company; 1986-07-01 to current/open; source msha-controller-operator-history