There's a nice looking WWI sniper scope on GunBroker - a Periscopic Prism Co. scope with the correct scope carrying case (properly numbered to the scope). I'd bid on the darn thing - if I had a WWI No.3 to put it on. Could be a good buy for someone on our board here.
Jim Z
RARE Sniper 'scope & Case, W.W. I British : Curios & Relics at GunBroker.com