# Relationship history for MSHA mine 2200503

Current hierarchy: **Kaiser Aluminum & Chemical Corp → Filtrol Corp → Polkville 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

- **controller_controls_mine:** U S Filter Corp → Polkville Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Filtrol Corp → Polkville Mine; 1979-01-01 to 1981-03-31; source msha-controller-operator-history
- **controller_controls_operator:** U S Filter Corp → Filtrol Corp; 1979-01-01 to 1981-03-31; source msha-controller-operator-history
- **operator_operates_mine:** Filtrol Corp → Polkville Mine; 1981-04-01 to 1981-12-14; source msha-controller-operator-history
- **controller_controls_mine:** Ashland Inc → Polkville Mine; 1981-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ashland Inc → Filtrol Corp; 1981-04-01 to 1981-12-14; source msha-controller-operator-history
- **operator_operates_mine:** Filtrol Corp → Polkville Mine; 1981-12-15 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kaiser Aluminum & Chemical Corp → Polkville Mine; 1981-12-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kaiser Aluminum & Chemical Corp → Filtrol Corp; 1981-12-15 to current/open; source msha-controller-operator-history