I get what you are saying Nigel.. that there might be other pack 'information' that is not included in the OPK. I have successfully used UNMAKE to copy a pack image to a PC and later used MAKE to successfully put it back again.
The following are extracts from the developers Read_me txt files and information...
DumpPack
~~~~~~~~
by Boris Cornet (reusing code from Horatios brilliant fast5 routine)
Dumppack produces an exact copy of a pack on the PC, mostly even if UNMAKE fails.
Since it uses low level pack access, it will also copy protected or corrupted packs.
The OPKs produced are sligthly different from standard OPK because all bytes on the pack are copied, the program does NOT stop at the <end-of-pack>-marker!
Please make sure the CommsLink is booted in and activate Psi2Win on the PC.
The program has an option to detect the pack size, but if you are copying an Organiser 1 pack or a pack with a corrupted pack header, you will have to specify the pack size.
SENDPACK
~~~~~~~~
by Jaap Scherphuis,
psion@jaapsch.net
This procedure will send an image of a pack through the comms link.
Before you run this program, make sure you have a comms link attached, and that the computer you have connected it to is running CL.
When you run PACKSEND, after a short pause you will be asked which pack to send. This can be pack B:, C: or D:. Simply press the appropriate letter, or ON to quit. Pack D: denotes the top slot, i.e. the comms link software.
While the image is sent, a counter counts down to 0 to indicate how much longer it will take. The pack image will be called PACK.OPK, and it is in the same format as the files produced by the developer kit's UNMAKE program.
ORG-Link_v2 Pack code buttons:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The four large buttons do exactly what the text on them says. Their actions replace the Psion MAKE and UNMAKE pack handling tools, and replicate their action precisely, but with two vital differences: 1, Psion limited this to pack C only, but with ORG-Link you can select pack B if you want, avoiding the need to risk physical and electrical stresses by moving packs when you don't want to; and 2, there is no 'AMAKE', you cannot append to a pack other than copying files to it in the normal way. It's easier, and safer, to make a clean pack image in one go, with BLDPACK. Add new files to that, then send the OPK file to a pack with ORG-Link. This method also prevents loss of space on EPROM or Flash packs caused by replacing old files.
Page 65 of the republished Technical Reference Manual
(here) has a pack section
PACK ID STRING
Every pack logged on the Organiser has a ten byte string for identification. This string is blown onto a blank pack by the Organiser during "sizing". It consists of an ID byte, a size byte, a 6 byte time string and a 2 byte checksum. Note that the time string (bits 2-7) is replaced by device information on bootable packs (see details in chapter External Interfacing on page 80).
You can of course examine the contents of an OPK with Jaaps OPK Editor..
This is a screen dump of the editor examining the pocket spreadsheet pack image.
.
OPK_Editor.png
.
Sincerely Martin