OK, so I found an older roll of 125 film on that auction site. I was the only bidder, so got it at $19.95. Band says develop before Sept. 1, 1912. Now I've used outdated film before, but this is ridiculous...
So, the spool. I posted above that I'd gotten a 103 spool, and it does in fact fit this camera. Now I received the 125-6 and guess what: Not only the spool the same size as 103 (meaning the table is wrong), it's apparently spooled on an actual 103 spool, which I measured right at 3.912". You can tell because the older spools were drilled right through, with the leader slot off-center so as not to go through the center hole, thereby to allow the removable winding key that the old Bullet #3's used to fit in there, and the end opposite the keyslot has three holes in a triangle for the old-style brass driver that the winding key screwed into.
Note that this is probably Kodak NC film; the Verichrome in the post above this one may have a totally different spool. I wonder if this was an early production run and they were trying to use up backstock of older spools.
(I forgot to mention to the seller that you can't send nitrate film through the mails. Nobody seems to have noticed, though.