# Relationship history for MSHA mine 3604850

Current hierarchy: **Wolfgang Robert -Lamar Swartzlander → Frailey Coal Company → Tracy 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:** Donaldson Coal Company → Tracy Slope; 1950-01-01 to 1976-12-01; source msha-controller-operator-history
- **controller_controls_mine:** Marlin  Wolfgang → Tracy Slope; 1950-01-01 to 1976-12-26; source msha-controller-operator-history
- **controller_controls_operator:** Marlin  Wolfgang → Donaldson Coal Company; 1950-01-01 to 1976-12-01; source msha-controller-operator-history
- **operator_operates_mine:** Frailey Coal Company → Tracy Slope; 1976-12-02 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Wolfgang Robert -Lamar Swartzlander Et Al → Tracy Slope; 1976-12-02 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Wolfgang Robert -Lamar Swartzlander Et Al → Frailey Coal Company; 1976-12-02 to current/open; source msha-controller-operator-history