# Relationship history for MSHA mine 1401240

Current hierarchy: **Superfos America Inc → Shears Inc → 152-922 PORTABLE**

- 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:** J H Shears' Sons Inc → 152-922 PORTABLE; 1950-01-01 to 1988-12-28; source msha-controller-operator-history
- **controller_controls_mine:** William  Shears Jr → 152-922 PORTABLE; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William  Shears Jr → J H Shears' Sons Inc; 1950-01-01 to 1988-12-28; source msha-controller-operator-history
- **operator_operates_mine:** Shears Inc → 152-922 PORTABLE; 1988-12-29 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Superfos America Inc → 152-922 PORTABLE; 1988-12-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Superfos America Inc → Shears Inc; 1988-12-29 to current/open; source msha-controller-operator-history