Pepe, I converted your pairs of images into color stereo red-cyan anaglyphs, sending the W700 card image to the left eye, and the ebay card image to the right eye. That's so that I could blow them up really large and see the differences, which immediately show up as shimmering within the visual field.
I think you're right about the blue pen/magic-marker dots. If you look closely at the packages marked with blue dots, the solder is more disorganized and uneven. I think those items (packages) have been replaced. Either that or someone had TRIED to replace them and failed to get them off the card. Also, if you look at the bottom edge of those two images, the W700 card is rev. A02, whereas the ebay card is rev. A00. I wouldn't be surprised if the ebay card is an engineering sample that's been reworked. Heaven knows where they got that from, perhaps factory discards. Please don't mention the seller here.
I've seen that before. For example, when the Intel 5350 wifi card, which had WiMAX, went out of production, ebay became flooded with engineering samples in which the WiMAX didn't work. The cards worked as normal wifi cards, but WiMAX uses a certificate-based scheme to authenticate service subscribers, and all of the certificates for the engineering samples had expired, and thus couldn't be used by subscribers. Some sellers/distributors had actually re-labeled (poorly) those cards before distributing them, because the original labels said "engineering sample -- not for resale." I'm sure that some of the sellers didn't even know they were relabeled. I had an authentic production card, from Toshiba as I recall, and from what I could tell from looking at the printed card labels in ebay listings at that time, virtually all the 5350 cards being offered were fakes -- they were relabled engineering samples. It was a total mess.
So if 3700M's are in short supply, it wouldn't surprise me if items like that surface on ebay. And if it is an engineering sample, then who knows whether it's compatible with the W700 even if it's a working card, given HP/Lenovo's pariticularness about various cards. You should probably look at the rev. number of the card from the photo in the listing, before buying. If it's A00, you may want to stay away.
And there are a LOT of layout/component differences between those two cards, which may not be readily apparent by just viewing the photos as you've laid them out. But the differences hit you in the face when viewing the photos in anaglyph form.
One other difference that I notice, if you look closely at the soldered points inside the white band that delineates the chip package, is that the solder on the right side of the ebay card looks more blob-like vs. your card, in which the solder is very crisp. It may mean nothing, or it may mean that someone has done some sort of reflow job on the ebay card.
One thing that's interesting about the lower (back) image of the ebay card is that there's some sort of production date sticker that looks like it's been partially torn off, or at least not filled out. Plus it has a totally nonsensical range of dates (the 3700M wasn't even in the womb in 2005). It just doesn't fit. So perhaps that's a partial give-away when looking at ebay listings.
Also, the ebay card says it was made in USA, vs. the W700 card which says made in China. I would think a pre-production card is more likely to have been made in the USA, since they probably had to be closer to the production facility during pre-production. So that may be another tip-off of a pre-production card.
The made in USA/CHINA mark also each have a number next to them, which is a much lower number for the USA-made card, another potential tip-off.
And, like you say, the ebay card is an earlier bios version, bios version being another potential tip-off.
If you look in the upper left area of the rear of the W700 card, there's what looks like a white stamped string T03. I don't know if that's an inspection mark or what, but if you look in the same area of the ebay card, there's instead something hand-written by a black magic marker. I'd swear that, if you tilt your head sideways to the left, it reads as "1-7-7". If that means January 7th, 2007, then it is a clear indication of a pre-production card, and THAT, along with the rev. A00 may get your money back. In any case, a hand-written annotation is seemingly another tip-off, since you're probably less likely to find that in a real production unit.
So, together, these may represent a constellation of features that may help you to distinguish a legit card from one that smells fishy.
Anyway, interesting stuff. I hope the luck of the draw is better next time with your ebay GPUs, if there is a next time.
Excellent photos, BTW.