Code:
nawk -F, 'NR==FNR{a[$1OFS$2OFS$3]++;next} a[$1OFS$2OFS$3]{b[$1OFS$2OFS$3]++;}
END{for(i in b){if(b[i]-1>0){print i"\t\t"b[i]-1}else{print "NEW :"i} } }' OFS=, 20111127.csv *.csv | sort -r
NEW :NE:571209,SHELF:18,SLOT:6
NEW :NE:566030,SHELF:2,SLOT:6
NEW :NE:564588,SHELF:5,SLOT:6
NEW :NE:556029,SHELF:8,SLOT:5
NEW :NE:510150,SHELF:9,SLOT:5
NEW :NE:508622,SHELF:10,SLOT:1
NEW :NE:20107650,SHELF:2,SLOT:4
NE:985068,SHELF:6,SLOT:4 1
NE:985068,SHELF:4,SLOT:1 2
NE:600866,SHELF:8,SLOT:3 20
NE:571209,SHELF:6,SLOT:1 51
NE:571209,SHELF:3,SLOT:3 14
NE:571209,SHELF:18,SLOT:2 1
NE:565808,SHELF:3,SLOT:4 1
NE:565229,SHELF:14,SLOT:1 2
NE:556029,SHELF:5,SLOT:2 3
NE:503284,SHELF:6,SLOT:3 14
NE:321636,SHELF:16,SLOT:1 4
NE:249314,SHELF:8,SLOT:1 6
NE:230388,SHELF:10,SLOT:2 2
NE:222268,SHELF:7,SLOT:6 34
NE:20173322,SHELF:5,SLOT:5 2
NE:20170632,SHELF:3,SLOT:3 12
nawk -F, 'NR==FNR{a[$1OFS$2OFS$3]++;next} a[$1OFS$2OFS$3]{b[$1OFS$2OFS$3]++;}
END{ for(i in a){if(a[i] && !b[i]){print "NEW: "i}} for(i in b){if(b[i])print i"\t\t"b[i]}}' OFS=, 20111127.csv *.csv
NE:556029,SHELF:8,SLOT:5 1
NE:566030,SHELF:2,SLOT:6 1
NE:222268,SHELF:7,SLOT:6 35
NE:564588,SHELF:5,SLOT:6 1
NE:20107650,SHELF:2,SLOT:4 1
NE:510150,SHELF:9,SLOT:5 1
NE:565808,SHELF:3,SLOT:4 2
NE:565229,SHELF:14,SLOT:1 3
NE:600866,SHELF:8,SLOT:3 21
NE:20170632,SHELF:3,SLOT:3 13
NE:985068,SHELF:4,SLOT:1 3
NE:571209,SHELF:3,SLOT:3 15
NE:571209,SHELF:6,SLOT:1 52
NE:321636,SHELF:16,SLOT:1 5
NE:571209,SHELF:18,SLOT:2 2
NE:508622,SHELF:10,SLOT:1 1
NE:230388,SHELF:10,SLOT:2 3
NE:571209,SHELF:18,SLOT:6 1
NE:556029,SHELF:5,SLOT:2 4
NE:503284,SHELF:6,SLOT:3 15
NE:20173322,SHELF:5,SLOT:5 3
NE:249314,SHELF:8,SLOT:1 7
NE:985068,SHELF:6,SLOT:4 2