A Folmer Graflex gravity-type synchronizer is a test device for checking shutter/flash synchronization timing. In practical terms, it was used to test shutter sync speeds so photographers or technicians could verify that a camera shutter fired in proper sync with flash equipment.

Based on the shared manual reference, it appears to be a Graflex accessory/service tool rather than a general photographic accessory. These devices were more relevant when flash synchronization needed mechanical testing and adjustment.

Today, it’s mainly of interest as a vintage camera collectible or reference tool. For most modern photographers, it has little practical use unless you’re servicing or studying older Graflex equipment and shutter sync systems.