Thanks to everyone for the comments.

 

It matters if whomever is doing the board assembly relies on inconsistent pin numbering between the board's pick-and-place file and their pick-and-place tool.

Nothing like the taste of your own foot on a Sunday morning. The thing is though with a diode if you draw the symbol correctly and omit any numbering then any problems are on their end and out of your control anyways. If the board house's datasheet doesn't make sense it would make more sense to contact them for clarification than try to find an answer elsewhere in my opinion. It may be possible they are not aware of any issues due to any number of reasons.

In all reality though out of curiosity I looked through datasheets on digikey and found most LED pins were not numbered. I also found of those that are numbered the cathode was actually numbered as pin 1 contrary to the diagram in #3.

 

There is supposed to be a 'çathod marking' in real life.

 

There is supposed to be a 'çathod marking' in real life.

There is usually some form of polarity marking -- it might mark the cathode on some parts and the anode on other parts (the datasheet should say). Unfortunately, for some thru-hole LEDs. the polarity was indicated by having one pin slightly longer than the other, which makes it real easy to orient the part when it is new. But once the part is installed and the leads are clipped, there was no longer any way to determine polarity visually. Most thru-hole LEDs had a slight flat on one side of the body, which required more careful inspection during assembly than the lead-length method, but at least you had a visual indicator that was retained after assembly. I always preferred LEDs that used both methods (which was very common, thankfully).

Increasingly, unfortunately, parts are manufactured with automatic pick-and-place assembly in mind in which case it isn't the ability to look at the part and determine polarity, but rather it's knowing how the part is oriented in the tape or the tray or whatever the carrier is. Some manufacturers choose to save the cost of individual package marking because they only intend to sell to markets that use automated assembly.

 

... if you draw the symbol correctly and omit any numbering then any problems are on their end and out of your control anyways...

Even if I can prove the error was at their end (which is never guaranteed), the shipping, taxes and duty fees are considerable (for a solo non-pro dude like me). They won't reimburse those expenses - and then there's the waste of 10-14 days.

Just to be clear; my original post was mainly to find out if "I read the datasheet correctly", or am I missing something due to lack of formal training.

I've since decided to use A instead of + when marking LEDs.

 

Even if I can prove the error was at their end (which is never guaranteed), the shipping, taxes and duty fees are considerable (for a solo non-pro dude like me). They won't reimburse those expenses - and then there's the waste of 10-14 days.

Just to be clear; my original post was mainly to find out if "I read the datasheet correctly", or am I missing something due to lack of formal training.

I've since decided to use A instead of + when marking LEDs.

I think "K" to mark the cathode is probably more common, but I could be wrong.

 

I think "K" to mark the cathode is probably more common, but I could be wrong.

I go for both “a” and “k”. I can always leave off one of them if there isn’t room. Kicad’s default identification (drawing a solid line around the cathode, with no line around the anode) is particularly poor.