Ciao I am one who loves the focal length on an M. I have an early 70s TE 4/135mm. I know what my TE can do, and I know what the recent APO 135 can do too, but it that one is long gone from my bag. I have found a few clean mid-1950s Hektor 4.5/135mm lenses (M and SM mount) at good prices. Will the Hektor differentiate itself enough from the TeleElmar? I am looking for a different fingerprint - a way to change my results simply by changing lenses. Or, are they, in reality, just too similar to justify doubling up on the focal length. (Albeit, the Hektors are all sub $250 anyway).