# Relationship history for MSHA mine 0403835

Current hierarchy: **EI DuPont De Nemours & Co Inc → Conoco Inc → Walker Mine**

- 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:** Ponderosa Mining & Development Corp → Walker Mine; 1950-01-01 to 1979-05-30; source msha-controller-operator-history
- **controller_controls_mine:** Tate M L → Walker Mine; 1950-01-01 to 1979-05-30; source msha-controller-operator-history
- **controller_controls_operator:** Tate M L → Ponderosa Mining & Development Corp; 1950-01-01 to 1979-05-30; source msha-controller-operator-history
- **controller_controls_mine:** Conoco Inc → Walker Mine; 1978-03-09 to 1981-08-05; source msha-controller-operator-history
- **operator_operates_mine:** Conoco Inc → Walker Mine; 1979-05-31 to 1981-08-05; source msha-controller-operator-history
- **controller_controls_operator:** Conoco Inc → Conoco Inc; 1979-05-31 to 1981-08-05; source msha-controller-operator-history
- **operator_operates_mine:** Conoco Inc → Walker Mine; 1981-08-06 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** EI DuPont De Nemours & Co Inc → Walker Mine; 1981-08-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** EI DuPont De Nemours & Co Inc → Conoco Inc; 1981-08-06 to current/open; source msha-controller-operator-history