Quote from: wattMaster on August 03, 2016, 03:22:06 PM

Why are date codes trade secrets?

Generally everything that the user does not really need to know about the product is assumed as a trade secret by some companies. And the date code belong to this type of information.
 The date codes may reveal, how the manufacturing is progressing (large batches made in a short time and then sold out for long time, or steady production), that may suggest the overall volume that is manufactured and so on. Plus it helps them conceal which lamp belong to which batch, so hiding batch problems from customers.

On the other hand many companies, mainly the quality minded, made intentionally the batch identification open and straight forward. With that they send a clear message: If there would be any problem with a batch that pops up only later in use, this identification will make sure such problem get recognized way sooner, all possibly affected pieces may be identified way sooner too, so the consequences of that problems could be greatly minimized.

So, in a way, if Sylvania date codes are not as much a trade secret, then the lamps should be of higher quality?

For the same money generally yes.
Defects appear everywhere and every time. But if the maker makes it difficult to trace back, it is harder for him to learn about their existence and so correct them. And that means way more affected production slips through.
But of course, the ability to track problems is an essential part to really eliminate them, but of course it is not the only essential part of that.
And if the system is known to the customers, it is way easier and cheaper to e.g. organize a recall of batches with e.g. some potentially dangerous defect. Because the easy and accurate identification allows to address only those affected and not much others. So such company then has not that big financial objections to issue such recall, so they do so way sooner and for way less severe problems.

But when someone brags "he does not need to track the defects because he does not have them", the only outcome is those defects are not only way more frequent, but a way more severe as well. The fact such maker refuses to know about the defects just makes them only "populate".

Sounds like a recipe for disaster!

Well, that is why all reputable makers do use some tracking system, most frequently in the form of the date code. What they differ is, how much they keep this information private and how much they make it easily understandable.

In the history there was another problem: How to mark the code in the cheapest way possible?
That is, where the date coding into some of the etch features (dots, lines, their position,...) became quite common - all was stamped at once.
Using alphanumeric coding would mean too many pieces of the stamp have to be reshuffled, making the stamp itself more complex and so prone to defects.
It suffices with just the same stamping, while it was easy to readjust on the stamp (make these dots/lines as inserts into the stamp and then move them along predefined positions when starting each batch). The dots/lines shifting means there are all the time the same components present on the stamp head, so e.g. none could become damaged or lost in storage or so.
When someone used number/letter codes, the system was made so, it suffices with as few letters/numbers as possible with still long enough repetition,...

Now, when the computers become the main controllers of the machinery, inkjet printing or laser engraving became the cheapest method (it allows any text/picture/logo alteration without need for any new part for the machine), just plain alphanumeric text became the most practical way (easy to read, so no decoding tables necessary, repetition periods could be easily made in 100's or even 10000's of years, so no risk of same products with the same date code but from different batches meeting together).

I think the real reason the codes are kept secret is because the handful of members here who do know how to date the lamps enjoy having that power over the other members. There's absolutely no other reason. The few date code systems I do know I have tried to shout from the mountaintops to help other members but of course I get enough backlash and the post/comment/picture gets deleted (not by me). This was especially a problem with the Gallery of Lights.

In recent years it becomes clear that the times are changing, the lampmakers seem to have become more relaxed about disclosing details of how to date their lamps.  Perhaps with the migration to LED, the old traditional products are no longer so important.  Also what is of interest to us as collectors are often so obsolete that there cannot possibly be any commercially valuable secrets any more. 

Many of the manufacturers have freely sent out details to those who ask, or even indicate the codes on their packaging or technical literature - and as TL8W mentions, even print both the old system and an inkjet code with the full date alongside each other, so even the most complex have now become rather easy to decipher!

Because of this, and that none of the main sites seemed interested to publish this information for various reasons, I have uploaded the ones that I know are in the public domain to my website - please have a look at the page http://lamptech.co.uk/Codes.htm

I hope this will help you and many others in deciphering the details of your old lamps!

Several of these have been worked out from real examples of old lamps, and could have some mistakes - in case anyone who knows them better than me does see an error that they would be willing to share with the rest of us, please do let me know.