# Relationship history for MSHA mine 4703612

Current hierarchy: **Martin Marietta Materials Inc → Barton Sand & Gravel Co → Portable Plant (Hoffmeister)**

- 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:** Tiller Corp → Portable Plant (Hoffmeister); 1983-03-01 to 2021-05-03; source msha-controller-operator-history
- **operator_operates_mine:** Barton Sand & Gravel Co → Portable Plant (Hoffmeister); 2011-06-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Tiller Corp → Barton Sand & Gravel Co; 2011-06-13 to 2021-05-03; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → Portable Plant (Hoffmeister); 2021-05-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Barton Sand & Gravel Co; 2021-05-04 to current/open; source msha-controller-operator-history