For clarification, when I refer to a MB piston mechanism, I mean the entire assembly as seen below:
An interesting point to note, is that there are three shared (or identical) components of the modern 146 and 149 mechanisms: the threaded spindle attached to the turning knob, what I'll call the piston rod that holds the seal, and the elastomer piston seal. Very early 60s 149s had a larger inside barrel diameter, and therefore a larger elastomer seal, I posted on this before, so will not belabor this point.
For comparison purposes, I photographed modern components of MB piston mechanisms: first photo has the the most modern 146 piston component, then an 80/90s component and a 70s component; second photo shows 149 components of a late 80s 149, early 70s 149, and very early 60s 149 (damaged).
When comparing the 146 components, one can clearly see the differences between the older and newer models, with the older model containing about 40% resin.
One can make the same observation with the 149 components. Note the the friction fit component is all resin except for the gold piston ring; it also uses a turning knob and piston rod/seal similar to the threaded mechanisms, but the seal is of a larger diameter. There is a newer piston mechanism on late 1990s/early 2000s 149s similar to the 146 mechanism.
Finally for a modern/vintage comparison here is a photo of the modern 146 piston mechanism alongside a 50s three-stage mechanism:
Edited by niksch, 03 April 2009 - 21:45.