[{_id:123,Customer:"A",State:"TX",City:"Houston",checksum:1111,IsBundled:false},{_id:1234,Customer:"B",State:"TX",City:"Houston",checksum:1111,IsBundled:false},{_id:12345,Customer:"C",State:"NY",City:"Buffalo",checksum:2222,IsBundled:false},{_id:123456,Customer:"D",State:"AB",City:"ABC",checksum:1111,IsBundled:false}]

db.collection.aggregate([{$group:{_id:"$checksum",count:{$sum:1},bundles:{$push:"$$ROOT"}}},{"$unwind":"$bundles"},{$set:{"bundles.IsBundled":{$gt:["$count",1]}}},{"$replaceRoot":{"newRoot":"$bundles"}}])