# Relationship history for MSHA mine 2901952

Current hierarchy: **H B Joint Venture (1976) & Property Holding Co-New → Carbon Coal Company → Carbon Ii**

- 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:** H B Joint Venture (1976) & Property Holding Co-New → Carbon Ii; 1977-08-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Carbon Coal Company → Carbon Ii; 1984-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** H B Joint Venture (1976) & Property Holding Co-New → Carbon Coal Company; 1984-02-01 to current/open; source msha-controller-operator-history