# Relationship history for MSHA mine 0501017

Current hierarchy: **Kelly  Coleman → Coleman Sand & Gravel → North Fork Sand & Gravel**

- 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:** A F Burkhard Company → North Fork Sand & Gravel; 1950-01-01 to 1979-05-23; source msha-controller-operator-history
- **controller_controls_mine:** Burkhard Albert F → North Fork Sand & Gravel; 1950-01-01 to 1979-05-23; source msha-controller-operator-history
- **controller_controls_operator:** Burkhard Albert F → A F Burkhard Company; 1950-01-01 to 1979-05-23; source msha-controller-operator-history
- **operator_operates_mine:** North Fork Sand & Gravel → North Fork Sand & Gravel; 1979-05-24 to 1990-01-29; source msha-controller-operator-history
- **controller_controls_mine:** Nation Bill & Glen King → North Fork Sand & Gravel; 1979-05-24 to 1990-01-29; source msha-controller-operator-history
- **controller_controls_operator:** Nation Bill & Glen King → North Fork Sand & Gravel; 1979-05-24 to 1990-01-29; source msha-controller-operator-history
- **operator_operates_mine:** Coleman Sand & Gravel → North Fork Sand & Gravel; 1990-01-30 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kelly  Coleman → North Fork Sand & Gravel; 1990-01-30 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kelly  Coleman → Coleman Sand & Gravel; 1990-01-30 to current/open; source msha-controller-operator-history