The former name for what is now known as Lillet Blanc, although the modern version is made to a different recipe without quinine to have more mass-market...
I have tried all of the well documented potential alternatives and then some. I have compared these with my own well preserved Kina Lillet (lilet). I would love to say that one of the proposed alternatives is the closest, but drum roll. In my personal and informed opinion modern Lillet Blanc is the closest and indeed very close. The bitter quinine that was removed has, over time been overstated. Off the shelf, the best compromise Vesper Martini is Vesper Martini No. 3 created Alessandro Palazzi.