The 242 I am looking at has a scalloped receiver and has a DOM of 1978 (Series C marked barrel set). It falls right in the 24V timeline, so I assume it is simply a standard 24V frame with the 242 Series C .410 barrel set. The stock does not have a Monte Carlo shape, it has a standard shotgun drop at the comb and heel.
Doing some research as to if the 242 frames will fit any other barrel sets built during the 24V Series C production. I'm finding that folks have put the .410/.410 sets on 24V frames with no problem, I wondering if the opposite is true.
The frame has a small firing pin up top, larger firing pin on bottom with the selector on the hammer.
It is an interesting shotgun, as the barrels are both Full and they give great patterns with 3" #6, one right on top of the other at 20yds. The bores polished up nicely.