David:
Aha! So, Hitchcock's set designer was actually not following the installation guide - not that there was an actual need to, because that fridge wouldn't have been hooked up to a gas supply, since there was no need for it to actually cool anything. Those cabinets above the Rope Servel would have been blocking the vent grille.
Sounds like bottom line is: You could vent one to the outside if you wanted to, but it wasn't felt necessary in the houses of the time, which were much more loosely built than today's.
If you ever get a chance to get a shot of the vent grille, I'd love to see the top of the unit. Servels fascinate me, and I know a lot from photos, but photos don't always show everything.
P.S.: You might be interested to know that in Rope, the plastic Servel badge on the door is intact and legible. But at one point in the movie, John Dall opens the fridge's door, and at that point, you can see that a rectangle of blue paint has been sprayed over the big Servel logo on the blue freezer door glass. The other wording ("Ice Cubes" and "Frozen Foods") on the freezer door glass was left visible. That big honkin' Servel logo was probably just a bit too distracting to be left in the shot. Product placement was not practiced all that much at the time; many products seen in midcentury movies have their logos concealed.
[this post was last edited: 12/16/2012-17:07]