I recently purchased a Linhof IV Technika which came with a Symmar 5,6/150mm. The lens has some fungus inside, nevertheless I love the image-quality despite that its very soft and has problems handling backlight situations. Thats why I purchased an additional lens on ebay and thought I will try out the famous Voigtlaender Apo-Lanthar 4.5 / 150mm and see what it's all about. I payed 550 US $ for a very clean lens which came in a Synchro-Compur shutter ... (maybe that was too much ? I am not very familiar with the value of vintage Voigtlander lenses). But when I inspected the lens I noticed that the front element has a serialnumber and the rear-element does not. Symmar lenses have the serial# engraved on both parts. Also the glass of the frontelement is perfectly clean but the rear shows several tiny airbubbles. Is it possible that the rearelement is not the original part ? Plus is there a way to figure out the age / production-year by means of the serial# ?

many thanks in advance for your comments