Internals for the SL-68 1 and the SL-68 2. There are several differences internally between these two pumps but the main differences are (probably other things I'm forgetting as well...):
SL-68 1:
•Longer powertube
•Different style valve retainer with larger OD flange on the front end.

SL-68 2:
Shorter powertube
Unique Valve retainer (both back and front have the same OD without a flaunge)