query: SELECT ?item ?catcode ?catnum ?catletter WHERE 
  { ?item p:P528 ?catalogstatement.
  ?catalogstatement ps:P528 ?catcode.
   ?catalogstatement pq:P972 wd:Q97143678 .
    BIND( xsd:integer(REPLACE(?catcode, "[a-zA-Z]", "")) AS ?catnum) BIND(REPLACE(?catcode,  "[0-9]*", "") AS ?catletter) 
  } ORDER BY ?catnum ?catletter