Is there any way of indentifying this file type?

Those are Mac OS 9-era metadata files which aren't supposed to be created or opened manually.

(259978)

You can also throw some Ruby at it via AppleScript. You would click on the Desktop, then press shift+cmd+U to open the Utilities folder and double-click the Apple Script Editor. Copy/paste the following code into the Script Editor, click the hammer icon to compile it, and then run. It will prompt you for an image and then tell you what the byte code for that image.

-- see https://en.wikipedia.org/wiki/List_of_file_signatures

use scripting additions

set imgFile to POSIX path of (choose file of type {"public.image"})
display dialog (my bytestring_from_Image(imgFile)) as text with title "File Signature Byte String"
return

on bytestring_from_Image(animage)
	return (do shell script "/usr/bin/env ruby <<'EOF' - " & animage's quoted form & "
puts File.new(ARGV[0]).read(4).unpack(\"H*\").join.chars.each_slice(2).map(&:join).join(' ')
EOF")
end bytestring_from_Image

With this output for a JPG image:

Then you search for the first four bytes above in the List of file signatures to determine what file type matches.

If you don't mind getting 'under the hood', the shell has a file command that can help identify a wide variety of files.

Open /Applications/Utilities/Terminal

In the window that opens, type:

file

followed by a space (the space is important)

Then drag the file in question from the Finder into this Terminal window, then press return.

file will examine the file and attempt to identify it and give a little info:

% file ./Proposal\ copy.pdf 
./Proposal\ copy.pdf: PDF document, version 1.6 (zip deflate encoded)

% file ./download.gif 
./download.gif: GIF image data, version 89a, 480 x 370

If you want to get even more detail, replace file with mdls:

% mdls ./download.gif 
_kMDItemDisplayNameWithExtensions                = "download.gif"
_kMDItemPhotoEmbedding                           = (
        {
        "vec_data" = {length = 1024, bytes = 0x79aa82ad 99a1ed2c 0798fa1c e52adfa8 ... 11ab291d cb1deda8 };
        "vec_dim" = 1;
        "vec_format" = 1;
        "vec_id" = 5037;
        "vec_version" = 5;
    }
)
kMDItemBitsPerSample                             = 32
kMDItemColorSpace                               = "RGB"
kMDItemContentCreationDate                       = 2025-04-01 19:04:47 +0000
kMDItemContentCreationDate_Ranking               = 2025-04-01 00:00:00 +0000
kMDItemContentModificationDate                   = 2025-04-01 19:04:47 +0000
kMDItemContentRating                             = 0
kMDItemContentType                               = "com.compuserve.gif"
kMDItemContentTypeTree                           = (
    "com.compuserve.gif",
    "public.image",
    "public.data",
    "public.item",
    "public.content"
)
kMDItemDateAdded                               = 2025-04-01 22:07:10 +0000
kMDItemDisplayName                               = "download.gif"
kMDItemDocumentIdentifier                        = 0
kMDItemEmbeddingVersion                          = 3
kMDItemFSContentChangeDate                       = 2025-04-01 19:04:47 +0000
kMDItemFSCreationDate                            = 2025-04-01 19:04:47 +0000
kMDItemFSCreatorCode                             = ""
kMDItemFSFinderFlags                             = 0
kMDItemFSHasCustomIcon                           = (null)
kMDItemFSInvisible                               = 0
kMDItemFSIsExtensionHidden                       = 0
kMDItemFSIsStationery                            = (null)
kMDItemFSLabel                               = 0
kMDItemFSName                               = "download.gif"
kMDItemFSNodeCount                               = (null)
kMDItemFSOwnerGroupID                            = 20
kMDItemFSOwnerUserID                             = 501
kMDItemFSSize                               = 506200
kMDItemFSTypeCode                               = ""
kMDItemHasAlphaChannel                           = 1
kMDItemInterestingDate_Ranking                   = 2025-04-01 00:00:00 +0000
kMDItemKind                               = "GIF image"
kMDItemLogicalSize                               = 506200
kMDItemOrientation                               = 0
kMDItemPhotosSceneClassificationMediaTypes       = (null)
kMDItemPhotosSceneClassificationTypedIdentifiers = (
    "1-492"
)
kMDItemPhotosSceneClassificationTypes            = (null)
kMDItemPhysicalSize                              = 507904
kMDItemPixelCount                               = 177600
kMDItemPixelHeight                               = 370
kMDItemPixelWidth                               = 480
kMDItemProfileName                               = "sRGB IEC61966-2.1"
kMDItemWhereFroms                               = (
    "blob:https://giphy.com/3ec89451-6c10-4e3f-f9ec-e3c0f908a974"
)

> hence the file type had been preserved in the file name rather than knocked off the end

Not necessarily. If they're really old QuickDraw PICTures, they likely date from pre-MacOS X times where filenames were never required to include the file type. In fact, we scoffed at MS-DOS and Windows users who were limited to 8.3 filenames, and while both later Windows versions and UNIX systems supported longer filenames they still used filename extensions, and both choked on spaces and certain other symbols.

The type was held internally to the file, so you could call any file anything you liked, without needing a filename extension, and the OS would inherently know what type of file it is (and therefore which application was needed to open it).

If you're having trouble opening them, try Graphic Converter which has an impressive list of image file types it supports.

Yes.

(259985)

https://forums.macrumors.com/threads/what-are-desktop-db-desktop-df-and-thevolumesettingsfolder-for.74287/

An older Apple QuickDraw picture (e.g. .pict) will also produce that all zero signature as I have one here that just did so. Try giving that file a .pict extension and see if it shows the image in the Finder, or opens in Apple's Preview application.