# Relationship history for MSHA mine 3601920

Current hierarchy: **Gary  Merwine; Terry L  Heim → M & H Coal Company → Mercury Slope**

- 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:** Mercury Coal Company → Mercury Slope; 1950-01-01 to 1994-06-28; source msha-controller-operator-history
- **controller_controls_mine:** Kenneth L  Richter → Mercury Slope; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kenneth L  Richter → Mercury Coal Company; 1950-01-01 to 1994-06-28; source msha-controller-operator-history
- **operator_operates_mine:** M & H Coal Company → Mercury Slope; 1994-06-29 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Gary  Merwine et al → Mercury Slope; 1994-06-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gary  Merwine et al → M & H Coal Company; 1994-06-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Terry L  Heim et al → M & H Coal Company; 1994-06-29 to current/open; source msha-controller-operator-history