Other vessels (AIS) mmsi value is not spec compliant.

[sbender9]

In vessels.self I get "mssi": "1234567"

In other vessels I get a stringValue:

      "mmsi": {
        "$source": "$source", 
        "timestamp": "1969-12-31T23:59:59.999Z", 
        "value": "368992000", 
        "values": {
          "$source": {
            "$source": "$source", 
            "timestamp": "1969-12-31T23:59:59.999Z", 
            "value": "368992000"
          }
        }
      },