I'd say: type. evtl. noch "article"
Welche Einträge stehen denn in der Spalte?

Guckst Du kurz mal da rein?: related discussion: Anhand dieser Regelung erfolgt die Einordnung...

Art.-Nr. is the header for the item number the item has got in a computer to generate orders or organize the stocking.

Sorry, the formatting got lost, but Art. Nr. is a subcolumn under Label and is indeed a Part No. whereas the Art coumn is between the Description column and the label column and all of the entires are either Etikett or Gravur. I'm puzzled though, as the things that are "Gravur" are not engravings.

Then: type

Part numbers , bar codes and the like can be lasered directly onto an article" Lasergravur".
Maybe they mean that.

I believe that the article number is on the article either as label or as lasered number...

Ah, I see. So "Type of marking"/"Labeling method" perhaps?

Yes, Sir!

Thanks, I realise, although in this case it needs to be Part No. for whatever reason, even if that is usually TKZ.