48638 is a postalcode and its consensus geometry is derived from uszcta.
{"mz:is_ceased":0,"geom:latitude":43.417038,"wof:name":"48638","counts:names_total":0,"wof:placetype":"postalcode","mz:is_current":1,"wof:hierarchy":[{"continent_id":102191575,"country_id":85633793,"county_id":102083725,"localadmin_id":404508805,"postalcode_id":554756835,"region_id":85688599}],"mz:is_deprecated":0,"lbl:latitude":43.418926,"geom:area":0.001948,"geom:longitude":-84.019603,"wof:id":554756835,"counts:concordances_total":1,"geom:type":"Polygon","wof:lastmodified":1611184281,"wof:belongsto":[102191575,85633793,102083725,404508805,85688599],"wof:concordances":{"gp:id":"26814710"},"wof:repo":"whosonfirst-data-postalcode-us","src:geom":"uszcta","wof:country":"US","counts:names_preferred":0,"geom:area_square_m":1.7500752257501E7,"wof:tags":[],"counts:names_variant":0,"wof:breaches":[],"edtf:inception":"uuuu","iso:country":"US","counts:names_languages":0,"geom:bbox":"-84.049288,43.392334,-83.993878,43.437338","wof:superseded_by":[],"wof:supersedes":[],"lbl:longitude":-84.018242,"wof:geomhash":"14d6d11f338945e1f34a759704a6a8d5","wof:parent_id":404508805,"wof:placetype_names":["postalcode"],"mz:hierarchy_label":1,"wof:placetype_id":470996387,"edtf:cessation":"uuuu","mz:postal_locality":"Saginaw"}