# Relationship history for MSHA mine 1512420

Current hierarchy: **Massey Lena & J B → Lena Coal Company → #16**

- 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:** Massey Lena & J B → #16; 1974-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Riggs Robert F → #16; 1979-10-01 to 1982-09-27; source msha-controller-operator-history
- **operator_operates_mine:** Push & Grunt Coal Company Inc → #16; 1980-06-01 to 1982-09-27; source msha-controller-operator-history
- **controller_controls_operator:** Riggs Robert F → Push & Grunt Coal Company Inc; 1980-06-01 to 1982-09-27; source msha-controller-operator-history
- **operator_operates_mine:** Lena Coal Company → #16; 1982-09-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Massey Lena & J B → Lena Coal Company; 1982-09-28 to current/open; source msha-controller-operator-history