Hi Wotan, yes IMHO there are some features to look for...
As far as the buffer pad on the last Puma, agreed likely added at some point.
Now I did received an interesting post from someone concerning this dagger,
"They were made in 1938 as prototypes. Puma had the idea to introduce a new pattern to sell thousands of brand new daggers to the Kriegsmarine. But German thriftiness just changed the reed-bundle pommel to the eagle pommel.
The Puma company told me just a handful were made and send to the involved offices of the Kriegsmarine and Wehrmacht.
Most of them were returned to the company after the introduction of the new pattern had failed."