I glanced through those links and generally saw overpriced watches in mediocre condition. However, I think that is inevitable if one is restricting one's search to stale C24 listings for watches from one brand in a narrow serial range. I almost never find anything interesting on C24.
After reading this far in the thread, I am thinking that perhaps you should just pick one you like and buy it. It's a very nice thought and I'm sure the gift will be greatly appreciated. (If you were buying the watch for a collector, my advice would be different.) Since you're not experienced, you can't really be expected to find a special collectible watch for a fair price.
If the birth-year restriction weren't an issue, you would certainly be able to pick up something nice from the sales listings on the forum. But it's a crap-shoot whether something in that serial number range will happen to be listed in the next couple of months. Maybe, maybe not.