In 1918 Oldenburg created a long-frontline service device for their combatant Friedrich August Cross 2nd Class's ribbon, here.
Unfortunately Oldenburg almost never made bestowals with award documents, and NONE have ever been observed for this "vor dem Feinde" bar. Like the Brunswick Long-Frontline service wreathed horse device (see that scan), it represents a required minimum of two years service at the front.
In practice, any holder of the "OK2" who wanted one apparently attached one on their own authority. Rank Lists make no distinction between a 2nd Class with or without this device.
This device is the ONLY German ribbon bar emblem that was PAINTED.
Size for 15mm width ribbon bars here.