21078 is a postalcode and its consensus geometry is derived from uszcta.
{"mz:is_ceased":0,"geom:latitude":39.565568,"wof:name":"21078","counts:names_total":0,"wof:placetype":"postalcode","mz:is_current":1,"wof:hierarchy":[{"continent_id":102191575,"country_id":85633793,"county_id":102082727,"postalcode_id":554707187,"region_id":85688501}],"mz:is_deprecated":0,"lbl:latitude":39.559229,"mz:postal_locality_alt":["Bel Air"],"geom:area":0.009645,"geom:longitude":-76.141929,"wof:id":554707187,"counts:concordances_total":1,"geom:type":"Polygon","wof:lastmodified":1611183145,"wof:belongsto":[102191575,85633793,102082727,85688501],"wof:concordances":{"gp:id":"12766449"},"wof:repo":"whosonfirst-data-postalcode-us","src:geom":"uszcta","wof:country":"US","counts:names_preferred":0,"gp:parent_id":"12588688","geom:area_square_m":9.1937379938912E7,"wof:tags":[],"counts:names_variant":0,"wof:breaches":[],"edtf:inception":"uuuu","iso:country":"US","counts:names_languages":0,"geom:bbox":"-76.240168,39.488263,-76.046966,39.623697","wof:superseded_by":[],"wof:supersedes":[],"lbl:longitude":-76.141248,"wof:geomhash":"876cacd6d1fa1c4ba440cea57464ef85","wof:parent_id":102082727,"wof:placetype_names":["postalcode"],"mz:hierarchy_label":1,"wof:placetype_id":470996387,"edtf:cessation":"uuuu","mz:postal_locality":"Havre De Grace"}