# Relationship history for MSHA mine 0505103

Current hierarchy: **Bill  Tezak → Colorado Quarries Inc → Screen Unit**

- 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

- **controller_controls_mine:** Bill  Tezak et al → Screen Unit; 1986-12-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Colorado Quarries Inc → Screen Unit; 2019-02-19 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bill  Tezak et al → Colorado Quarries Inc; 2019-02-19 to current/open; source msha-controller-operator-history