Hello Corey,
See my response below.

--- On Thu, 8/19/10, Corey Bailey <[log in to unmask]> wrote:
From: Corey Bailey <[log in to unmask]>
Subject: Re: [ARSCLIST] help: 16MM mag sound film
To: [log in to unmask]
Date: Thursday, August 19, 2010, 10:37 PM

Hi All,

17.5 mm was mostly a European format most popular in Germany and France. I?ve seen some Italian & Hebrew foreign dubs on 17.5 but not as much as the other two. Thus, most of the 17.5 I have encountered is PAL with a few NTSC exceptions for elements made for the US market. All of the 17.5 I have encountered runs at film speed be it NTSC or PAL and virtually all of it is single track Mono. I never understood the rationale for this format <snip>

If I'm not mistaken, I think I recall 17.5 being used by the film sound effects department at CBS Studio Center in Studio City. By having all those sound effects "units" in that format,  it literally cut in half the cost of the film stock, and in running it at half the speed of 35MM at 45ft/min, it cut the cost in half again.  I know the sound effects editors hated it and call it "spaghetti", since it would easily curl up on itself if it wasn't held taunt.
I think the Larson Studios and others in Hollywood can still handle it.