Documenting unlabeled Gunne Sax

[poisson_rouge]

Hello!! I found what I am 99.9% sure is an unlabeled Gunne Sax dress but I need some help figuring out how to document it. The dress is professionally made and unlabeled except for some conspicuous tags at the base of the zipper (pictured). It is almost identical to this one on ebay that is labeled, except the for the cuffs of the sleeves. But otherwise the size, length, laces, fabric, pearl buttons -- everything else is the same. I don't think it was an alteration because it looks like the same stitching on other lace areas and there were alterations to the hem and some extra lace tacked on that had a pretty obvious and heavy hand. I know Gunne Sax incorporated lots of little variations in dresses and I found other GS styles with these sleeves so I'm confident the label was just taken off at some point, except... I also found two other dresses online that are matches in every way including the sleeves that are also mysteriously unlabeled (???)

1) Are there any Gunne nerds who have a take on what's going on with the matching unlabeled dresses?

2) Assuming it is an official Gunne Sax, how can I try to document this piece? Should I be looking for an original ad or is it usually enough to have found matching pieces that are labeled? Is this something I would contact the design house about?

Thanks for any insight or direction!!