Just adding a +1 to @IvanDobsky - this is an area where Discogs is a much better reference DB.
I stayed adding matrix scans recently when I realized they were useful. But interesting that it took a long time - I think most people (including me) follow the example that’s been set, so we have a 
and 
situation. Once we have more matrix pics in the DB I think we will start having even more added!
To piggy back on this, knowing the exact pressing of my CD [in my collection] is very important to me, but I’ve noticed the same usage as IvanDobsky. I do my best to try to add this info or clarify it where it exists (on top of adding scans of the matrix). I often think about how great it would be to get a field for this (https://tickets.metabrainz.org/browse/STYLE-781) and guidelines to help us standardize: where to begin/end, spacing, pressed chars (A01), bizarre chars (⟡), barcodes, mastering and mould source ID codes (SIDs).
Another curiosity of mine is similar but different mastering and mould codes, often called variants, and how to determine which should be grouped together in a release or separated into two releases. Discogs generally does quite well with this, however I’ve seen some questionably different variants on the same release before.
The more of us who do it, the more it will happen. Many people just want artwork and tagging. Or they think we are mad even caring about the factories. 
There is a growing number of people who live in both Discogs and MB camps and have learnt more of these little details.
Getting any changes done round here take an age. It would take barely any time to add a “matrix” art type. Doesn’t happen. So we have to make up our own standard of “medium+other”.
I’ll add relationships for the Pressing \ Manufacturing labels into the actual Releases as often as I can.
The rest has to be in the annotation. I like to write in the actual DiscID that links to the Matrix and SID details. Mainly due to those old releases from Pre-NGS which have 20 unverified discIDs attached. The same batch attached to ALL the releases in an RG. 
By also noting the DiscIDs with matrixes it helps to show what is and is not common between pressings. This way I have found mistakes when the wrong discID had been used to set track times. Artists like Bjork, Enya, Floyd who have very different early pressings of a CD. A combo of Matrix and DiscIDs allow these to really be identified.
For that one I focus on the manufacturer. Who made it? We know a production line once started may last decades. I don’t always agree with Discogs as I focus on the manufacturer. It also depends on how many variants are already listed on this one Release Group.
).I also have releases where there is no point in adding the matrix. A release I know was only done in a small production run in one country. Never repressed. We have over 100 release variants of The Dark Side of the Moon as it was made in so many different place in so many different ways so details are needed. But some of my old punk CDs only ever had a small run so no need to try and tell them apart.
You may also want to have a nose at some of the Manufacturing Labels. Both myself, @ernstlx and others have added a lot more details into some of these. Bits of history, linking the companies and owners, name changes. And a start of better identification methods. Much of it is cribbed from Discogs, discs in hand, Steve Hoffmann, etc.
I would love somewhere to put a chart of SID codes as these can be used to nail the factories. For now I add some to the Label\Manufacturer page.
Now I have said @ernstlx a third time I am expecting him to appear and chime in here. A fellow addict 
If you look at CDs I’ve edited you’ll always find pictures of them, but in general I’d recommend checking Discogs. It’s much more about matrix details, because (as mentioned above) their versions are distinguished even if the content is the same.
You can determine the plant from the codes. If it’s from the same plant, it usually have the same content (except in very rare cases) and should be considered as the same release. If it’s from another plant, it most likely has a different DiscID and therefore different content.¹ (not all users will agree, I know)
Discogs guidelines are very helpful for identifying the plant (company specific codes or since 1994 mastering SIDs).
I’ve seen many questionable variants on Discogs and tried to fix some of them 
That’s really great. I will do that in the future too (…like in your example. So far I’ve only done it when multiple disc IDs already existed)
You never know if the artist will become famous and countless re-releases will come onto the market… 
¹) It’s always about the mastering SID, because the actual content only depends on this. The actual manufacturer (pressing → mould SID) is not responsible for the content, but often causes changes in artwork (at least the disc face was also printed there)
Great conversation!!! Maybe after I’m done entering all my music …I’ll start entering this extra data…I’ve already bought a magnifying glass…LOL 
I recommend a small microscope - very useful! (I’ve got it recommended by @IvanDobsky once)
But a magnifying glass is necessary too.
… see Release country of CD/Vinyl releases / Release identification methods - #139 by IvanDobsky (offer is still on stock)
That’s the reason I started doing it - to bring clarity to pre-NGS mess. But do it more and more now on any release I add or update. Be good to get more people in the habit (I know I am not the only one doing this)
Yeah - but usually something else happens on the artwork, and they find a few extras to shove on a “deluxe edition”. 
In most cases I am getting more and more complete with my releases. Now the scanner is alive again I’ll often add the extras, and the more I know people want to see it, the more it will appear. In my own collection I have opened up a rather large spreadsheet with my matrix, SIDs, discIDs and other notes. Cross linked with Discogs and MB.
This is a must to read that SID code. And so cheap to find on Ebay. Also great fun for other things. I’ve also used mine to study a fancy fossil I found, insects, plants… 
Warning - this becomes addictive. 
I can only dream of that. I still have more than 2000 albums ahead of me (in my digital collection*) and I want to start with my vinyl collection shortly…
*) worse than untagged - tagged with random information
… I’ve made a spreadsheet too, but I’ll have to transfer it to a database soon. And I use “places” on MB to write down what I know about a plant. (see EDC Germany - MusicBrainz for example)
Regarding microscope:
… and it’s even suitable for outdoor use. It comes in a sturdy case and can be displayed on your phone (I rarely use it that way, and it should be treated with care anyway!)
Yes!
I only have a third of your CDs, but what I meant is each new one I add gets more details. The first CDs I added would just be track list and front\back scans. Now it is full scans, matrix scan, matrix info, and as many relationships as I can rip out of the booklet. From Guitar player to Copyright, from CD Manufacturer to booklet writer.
This means I keep going back to old Releases I own and blitzing more data. Making it a never ending rabbit hole. The more I learn the more accurate things become.
The spreadsheet may well morph into a database. All these albums are already in an SQL database in my KODI Media Centre which is the most obvious candidate to expand. Just imagine a KODI addon that lets you gather all your CDs printed at EMI SWINDON and bring up pages of data about the history of the factory…
Many of my CDs are from the 1990s when plants were changing hands. So Label is needed as PDO → PMDC → PDC → etc. This does means an ultimate Release will have Place and Label added for Glass Mastered, Pressed and Manufactured.
Next time you are in the woods, point it at the moss on a tree. There is a little world hidden in there.
I try to enter everything necessary and the longer I do this, the more data I find necessary…
I’ve got KODI too but I don’t think I will expand it to matrix information. I want to be independent of versions and devices. Rather, I will try to save this information in the files and only display it in KODI.¹ For my matrix data I will create a separate db.
¹) with _releaseannotation displaying a comment
… and every place will have relationships to every owner and every brand that was used 
I’ll try… 
It was your comment about “make a database” that got me thinking. KODI has that SQL Database with all my CD in it just begging for an extra table to be added with all this mad data. We are talking very long term project…
I can only support the urge for more information.
If I scan my CDs, I do it always with the matrix. Helped me to avoid some surprises already.
Specifically for this need i bought a CCD scanner, to get a clear scan of the matrix. 
…in fact it would need only one additional table for included discs, because the release and all release related data is already available. I don’t see an overriding benefit right now, but this way it should be easy to maintain, and I don’t see a downside either.
Thanks for this idea, thank you once again!
Now I looked up what a CCD scanner is…
I don’t think I have one. Actually I’ve got an awful scanner (very cheap, probably a CIS scanner), but it is sufficient for documentation (awful colors, still good depth of field). I will probably keep it, but if i ever buy a new one, I will look for a CCD scanner.
(For my records I will switch to photo technology. That looks more promising to me.)
Scanning vinyl is a pain in the ass, tbh. I do it only from time to time.
Tell me more about the photography technology, if it’s more than just taking good pictures. 
Wow this is awesome. This looks amazing. If you can avoid reflections with it, perfect! need to take a closer look at this. And according to google it’s affordable. THANKS
Don’t be too euphoric - I’ll try it first. I’m not entirely sure if it fully works. This copy stand has point light sources. Although the light comes from 2 directions, I’m not sure if everything is illuminated evenly. And I will first see if there are no reflections…
Agreed @slipmaxim! I have been struggling to figure out how to get good vinyl images (they don’t fit in my CanoScan 9000F). Every time I upload crooked images with reflections I cringe a bit, but it’s the best I have right now. I would love to hear anyone’s experience or recommendations for a copy stand.
I feel you! I have the same scanner but MK II.
I managed to scan gatefold covers like this:
But it’s very time consuming tbh, because you need to stitch pictures together.