Field "catalog number" of GUDID for US is equivalent to field "Reference-catalogue number" in EUDAMED for EU. This information is captured in Device.partNumber defined as "The part number or catalog number of the device". 

We had attempted to capture it within the identifier element in DeviceDefinition, using a special value of type of identifier for that purpose. But this is inconsistent with Device, so we have withdrawn this special value of identifier type, before the tracker would be approved. 

The change needed here is to add an element to DeviceDefinition identical to the one of Device.

Add at the top level of DeviceDefinition, the element "partNumber":

partNumber 0..1 string    "The part number or catalog number of the device"