# Relationship history for MSHA mine 3608902

Current hierarchy: **Kendra K Folk; Melinda F Gibson; Beverly A Critchfield → Keystone Lime Company Inc → Eichorn 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

- **controller_controls_mine:** Mark  Folk → Eichorn Quarry; 1950-01-01 to 2025-08-14; source msha-controller-operator-history
- **operator_operates_mine:** Keystone Lime Company Inc → Eichorn Quarry; 2001-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mark  Folk → Keystone Lime Company Inc; 2001-01-01 to 2025-08-14; source msha-controller-operator-history
- **controller_controls_mine:** Melinda F Gibson et al → Eichorn Quarry; 2025-08-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Melinda F Gibson et al → Keystone Lime Company Inc; 2025-08-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Beverly A Critchfield et al → Keystone Lime Company Inc; 2025-08-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kendra K Folk et al → Keystone Lime Company Inc; 2025-08-15 to current/open; source msha-controller-operator-history