# Relationship history for MSHA mine 3605508

Current hierarchy: **Polycor Inc → Pennsylvania Granite Corp. → American Black Quarry**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Pennsylvania Granite Corp → American Black Quarry; 1950-01-01 to 1988-09-30; source msha-controller-operator-history
- **controller_controls_mine:** Stanley  Wilbur → American Black Quarry; 1950-01-01 to 1988-09-30; source msha-controller-operator-history
- **controller_controls_operator:** Stanley  Wilbur → Pennsylvania Granite Corp; 1950-01-01 to 1988-09-30; source msha-controller-operator-history
- **operator_operates_mine:** Pennsylvania Granite Corp → American Black Quarry; 1988-10-01 to 1997-10-31; source msha-controller-operator-history
- **controller_controls_mine:** Keystone Memorial Co & Childs & Childs Granite Com → American Black Quarry; 1988-10-01 to 1997-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Keystone Memorial Co & Childs & Childs Granite Com → Pennsylvania Granite Corp; 1988-10-01 to 1997-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Pennsylvania Granite Corp. → American Black Quarry; 1997-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kurt M  Swenson → American Black Quarry; 1997-11-01 to 2016-09-20; source msha-controller-operator-history
- **controller_controls_operator:** Kurt M  Swenson → Pennsylvania Granite Corp.; 1997-11-01 to 2016-09-20; source msha-controller-operator-history
- **controller_controls_mine:** Polycor Inc → American Black Quarry; 2016-09-21 to 2023-07-04; source msha-controller-operator-history
- **controller_controls_operator:** Polycor Inc → Pennsylvania Granite Corp.; 2016-09-21 to 2023-07-04; source msha-controller-operator-history
- **controller_controls_mine:** TorQuest Partners Inc → American Black Quarry; 2023-07-05 to 2023-08-31; source msha-controller-operator-history
- **controller_controls_operator:** TorQuest Partners Inc → Pennsylvania Granite Corp.; 2023-07-05 to 2023-08-31; source msha-controller-operator-history
- **controller_controls_mine:** Polycor Inc → American Black Quarry; 2023-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Polycor Inc → Pennsylvania Granite Corp.; 2023-09-01 to current/open; source msha-controller-operator-history