We have a scanned copy of the index for this file which you can download and then look up to work out which letters interest you. The "Names Index" on the index file which you can download below starts on page 27 (or page 28 of the pdf file).
The letters start with letter #1 at frame 14 (on Ancestry.com). The last letter is #643.
Note that we have recently added a link to the SROWA website so that you can download this register - see below.