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I have a PC game CD twice here. The ISO images on the disks are matching exactly.

Is there any unique ID on the disks which make it possible to distinguish between them?

Somewhere in the meta data?

There is nothing special I want to achieve. I am simply interested in it.

I hope it's clear what I want to do. I want to distinguish two CDs which are carrying the same data.

javanerd
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    If the ISO files matches then there isn't and can't be any difference. – ChanganAuto May 22 '23 at 09:03
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    @ChanganAuto Are you sure? There can be more than an ISO on a CD. For example additional audio tracks... – javanerd May 22 '23 at 09:09
  • An ISO image is a 1:1 copy of the contents of optical media so what you asking is nonsensical. Sure, you can write any number of ISO files "as is" in another media, optical or otherwise, like any other file or container file (zip, rar, etc) but that's irrelevant but also confusing! Please [edit] and describe what you mean by "The ISO images on the disks are matching exactly" and how is it related with "I have a PC game CD twice".ç – ChanganAuto May 22 '23 at 09:17
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    Sure, CDs can have quite some data that is not part of the user data area. Also, [check this](https://superuser.com/questions/217890/where-is-the-serial-number-of-the-dvd-cd-writer-stored-on-the-cd)—it may not even be digitally readable. – Daniel B May 22 '23 at 09:25
  • DVD/CD have a unique bar code type identification around the hub of the disc that can be read with a disc identification application, but isn't readable by a person. Used for commercial purposes. – harrymc May 22 '23 at 09:29
  • @DanielB (and harrymc) I think you're trowing wood to the OP's confusion fire. Irrespective of the clarification I asked for, 2 identical copies of the same commercial CD-ROM don't have any unique identifier like a serial number. If the bar code is different then one of them is a counterfeit. – ChanganAuto May 22 '23 at 09:33
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    "Is there any unique ID on the disks which make it possible to distinguish between them?" - No; It's not possible to distinguish to identical copies of an ISO. – Ramhound May 22 '23 at 14:27
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    @ChanganAuto it may not be a "unique identifier". The point here is that ISO dumps that are identical merely means that the their source media *give the same ISO dump*. The ISO dump may not necessarily be all the data that exists on the media (and I am not referring to carving or whatsoever, but the fact that direct read with e.g. `dd` does not necessarily give you everything on the disc). (Direct might not be the right wording but you get the sense.) – Tom Yan May 23 '23 at 05:15

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If a publisher wanted to do this, nothing is stopping them, except...

Bulk disk creation is essentially stamping the disks, so duplicate content doesn't really fit into that method.

To write unique values to each disk means writing each disk individually: possible, but not commonly done.

music2myear
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