So, I just joined the club today. My CZJ Sonnar 1.5/5 cm in M39 has arrived this afternoon. Here it is with it's "sibling", a CZJ Sonnar 2/5 cm in M39.
The optical assembly is brass with corresponding serial number engraved, there is lower case "m", small focus triangle, and also the two adjacent screws on the focusing ring. But, it has ears on the aperture ring and commas as separators. Even though, so does my 2/50 Sonnar, and that is a 100% original wartime lens.
Plus, there is a small and faint engraving on the rangefinder coupling ring. It says "Re" in script, and appears to have been done by hand, possibly by technician during assembly or repair.
The apperture ring is dented in one place, but it is moving okay. The glass seems to be okay with some cleaning marks on the front element.
So, is it the real deal, or a very, very, very well made fake? :-D