1907 magazine pouch questions|General Discussions & Questions|Forum|Winchester Collector

So I have a Heiser plain leather double magazine pouch for 10 round factory magazines.  I saw a Heiser carved single pouch and got it too.  It does not fit the 10 round mags but does fit two 5-round magazines.  The markings on the back of the these two pouches each has a 6 and the plain pouch has a 1 and the carved pouch has a 3.  Does the forum think the slightly smaller pouch is for 2 five round? Or is it for some magazine that I have not seen or imagined yet?