# Relationship history for MSHA mine 3608726

Current hierarchy: **L & D Management Inc → Keystone Quarry Inc → Keystone 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Keystone Landfill Inc → Keystone Quarry; 1998-04-01 to 2004-03-09; source msha-controller-operator-history
- **controller_controls_mine:** L & D Management Inc → Keystone Quarry; 1998-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** L & D Management Inc → Keystone Landfill Inc; 1998-04-01 to 2004-03-09; source msha-controller-operator-history
- **controller_controls_mine:** L & D Management Inc → Keystone Quarry; 1999-08-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Keystone Quarry Inc → Keystone Quarry; 2004-03-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** L & D Management Inc → Keystone Quarry Inc; 2004-03-10 to current/open; source msha-controller-operator-history