Nostalgia is an interesting one. First off, it's lighter than you might expect. It has none of the heavy floral or leather of K10, and is not as striking as Lonestar Memories.
The leather note most reminds me of CdG's Skai, if that is any help. Its sort of a lighter, more synthetic leather smell, with a good dose of vanilla in the drydown. There are some topnotes that are similar to Black - Nostalgia has a turpentine, petrol note in the top that is pretty distinctive, but it leaves quickly. The remaining notes focus on that strange, almost watery leather note. The whole thing is an interesting and pretty nice fragrance, but I always wish that it had more presence and better longevity. Given those limitations though, its a fragrance that I like a lot and wear occasionally. Not an everyday fragrance, but one that I always enjoy when I pull it out. I recommend finding a sample.