This is the report I created for this, based upon serial numbers:
Select tsysAssetTypes.AssetTypeIcon10 As icon,
tblAssets.AssetID,
tblAssets.AssetName,
tblAssetCustom.Serialnumber,
tblAssets.Domain,
tblAssets.Username,
tblAssets.Userdomain,
tsysAssetTypes.AssetTypename As Type,
tblAssets.IPAddress,
tblAssets.Description,
tblAssetCustom.Manufacturer,
tblAssetCustom.Model,
tblAssetCustom.Location,
tsysIPLocations.IPLocation,
tblAssets.Firstseen As [Created at],
tblAssets.Lastseen As [Last successful scan]
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tblAssets.Assettype = tsysAssetTypes.AssetType
Inner Join (Select Count(tblAssetCustom.AssetID) As Total,
Coalesce(tblAssetCustom.Serialnumber, N'') As Serial
From tblAssetCustom
Where tblAssetCustom.State = 1
Group By Coalesce(tblAssetCustom.Serialnumber, N'')
Having Count(tblAssetCustom.AssetID) > 1 And
Coalesce(tblAssetCustom.Serialnumber, N'') <> '') As Dups On
tblAssetCustom.Serialnumber = Dups.Serial
Left Outer Join tsysIPLocations On tblAssets.LocationID =
tsysIPLocations.LocationID
Where tblAssetCustom.State = 1
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Union Home Mortgage's "Lansweeper Guy"
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