# Relationship history for MSHA mine 2500906

Current hierarchy: **Mike  Hollibaugh → Ritterbush Construction Inc → Dredge No 1**

- 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:** Harry Ritterbush Contractor → Dredge No 1; 1978-12-01 to 1983-12-04; source msha-controller-operator-history
- **controller_controls_mine:** Ritterbush Harry → Dredge No 1; 1978-12-01 to 1983-12-04; source msha-controller-operator-history
- **controller_controls_operator:** Ritterbush Harry → Harry Ritterbush Contractor; 1978-12-01 to 1983-12-04; source msha-controller-operator-history
- **operator_operates_mine:** Ritterbush Construction Inc → Dredge No 1; 1983-12-05 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Mike  Hollibaugh → Dredge No 1; 1983-12-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mike  Hollibaugh → Ritterbush Construction Inc; 1983-12-05 to current/open; source msha-controller-operator-history