# Relationship history for MSHA mine 1507160

Current hierarchy: **Kassity Robert F → Trancas Mining Company → Martin Surface 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:** Saint Johnsbury Mining Corp → Martin Surface Mine; 1974-01-01 to 1974-12-08; source msha-controller-operator-history
- **controller_controls_mine:** Donn A  Chickering → Martin Surface Mine; 1974-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Donn A  Chickering → Saint Johnsbury Mining Corp; 1974-01-01 to 1974-12-08; source msha-controller-operator-history
- **operator_operates_mine:** Trancas Mining Company → Martin Surface Mine; 1974-12-09 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Kassity Robert F → Martin Surface Mine; 1974-12-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kassity Robert F → Trancas Mining Company; 1974-12-09 to current/open; source msha-controller-operator-history