The KAC-992 probe antenna coupler is a unique piece of equipment in that it is mounted on the exterior of the aircraft. Therefore, it is exposed to the severe elements experienced in flight. When they were manufactured, the dataplate was attached to the exterior of the unit with no special consideration for this exposure. The manufacturer also placed the dataplate in a position on the coupler that is directly in line with the rear attaching clamp. Because of these two conditions, the dataplate falls off and is lost in most cases.
The manufacturer will not issue new dataplates even though they are aware of this unfortunate circumstance. Therefore, the market is left with functioning and useful units that cannot be certified with an FAA approved maintenance release because the dataplate is missing and no method exists to obtain a new one.