This layer combines the Parcels_Current layer (sourced from DPW) with another layer which attempts to find a current parcel boundary to associate with retired parcels. Parcels_Current contains recently retired parcel boundaries but this layer attempts to also map older parcels that may have been retired for many years or decades (and where we have no digital record of the exact parcel boundary). It does this by analyzing the history of parcel splits and mergers - if a parcel has gone through a number of splits and mergers the geography used will be a dissolve of all current parcels that contain the original parcel in its splits and merger history. As such the boundary may often be imperfect, it will always be on the correct block but it's possible that the boundary will be larger than the original or adjacent to it. E.g. parcel 001 is split into 010, 011 and 012, parcel 012 is then merged with parcel 002; parcel 001 will then be given the combined geography of 010, 011, 012 and 002. For these older parcels the geography used may be looked upon as a best guess boundary, useful for mapping otherwise unmappable, retired parcels but imperfect.