# Relationship history for MSHA mine 1600915

Current hierarchy: **Gay Billy & Keith Sistrunk → K & G Materials → K & G Materials**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Bert'S Sand & Gravel → K & G Materials; 1950-01-01 to 1979-04-30; source msha-controller-operator-history
- **controller_controls_mine:** Bert'S Sand & Gravel → K & G Materials; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bert'S Sand & Gravel → Bert'S Sand & Gravel; 1950-01-01 to 1979-04-30; source msha-controller-operator-history
- **operator_operates_mine:** K & G Materials → K & G Materials; 1979-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Gay Billy & Keith Sistrunk → K & G Materials; 1979-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gay Billy & Keith Sistrunk → K & G Materials; 1979-05-01 to current/open; source msha-controller-operator-history