When taking a snapshot of a volume that has partition (MBR or GPT) it contains a unique identification. MBR uses disk signatures and GPT uses GUIDs (Global Unique IDentifiers). See the two examples below.
w
These unique identifiers represent the signature of a particular disk. When creating a snapshot it creates a block-for-block representation of the original volume that includes the unique identifications. The example below illustrates Volume 1 and Snapshot 1 which shows each have the same ID = 9A802B99. Just as it shows Snapshot 1 represents Volume 1 block-for-block. The process of creating a snapshot does not re-signature the volume.