I'm looking at two 50mm DR Summicrons. One says 5cm with GmbH inscriptions are upper and lower case; the other says 50 (no units or GmbH) and all the inscriptions are upper case letters. Distance scale on the barrel are also different. Did Leica make two versions of this lens? I tried searching for any information regarding this, but am not making much progress. Hopefully one of you knows. Thanks!