I bought an Elmar 3.5 50mm lens on Ebay (listed as such) to go with the IIIf I got a few weeks ago but feel it's most likely a fake, based on the strange focusing lever. The lever is non-Leica-like and most levers I see all are the same. The few instances where I did see a similar lever online usually point me to fake ones.. In locked position, the lever is at 11 o'clock, which may be another "trick" they were using to make it look authentic. The serial number is on the ring (visible in my picture) but it's quite short (5 digits - the first one not readable). I don't see any other obvious giveaways. There are heavy scuff marks on the side of the barrel, which appears to be brass underneath the chrome).
This auction (from 2006) lists the same one as an Elmar 50mm 3.5
http://www.liveauctioneers.com/item/2453324
This page has the same lens but has it on a fake Leica II.
http://www.cameraquest.com/leica_II_fake.htm
I'm contacting the seller to arrange a return but I wanted your insight first. I very much doubt Leitz made multiple designs of the lever.