# Relationship history for MSHA mine 4102736

Current hierarchy: **Shelton Thomas → L T T Sand & Gravel Inc → L T T Humble Dredge**

- 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

- **operator_operates_mine:** Bishop Sand & Gravel Company → L T T Humble Dredge; 1950-01-01 to 1979-04-15; source msha-controller-operator-history
- **controller_controls_mine:** Bishop John T → L T T Humble Dredge; 1950-01-01 to 1979-04-15; source msha-controller-operator-history
- **controller_controls_operator:** Bishop John T → Bishop Sand & Gravel Company; 1950-01-01 to 1979-04-15; source msha-controller-operator-history
- **operator_operates_mine:** L T T Sand & Gravel Inc → L T T Humble Dredge; 1979-04-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Shelton Thomas → L T T Humble Dredge; 1979-04-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Shelton Thomas → L T T Sand & Gravel Inc; 1979-04-16 to current/open; source msha-controller-operator-history