R. Huna said, As long as the surface of the sides(19) of the tefillin is whole they are valid. R. Hisda said, If two [sides](20) were split they are still valid; but if three, they are invalid. Said to him Raba, Your ruling that if two [sides] were split they are still valid is true only if [the rents were] not facing each other,(21) but if they were facing each other they are invalid. And even if they were facing each other [they are invalid] only if they were new(22) [tefillin], but if they were old it would not matter.
Notes: (19) I.e., the external sides of the box, or the sides which form the divisions between the compartments. (20) According to Maim. (v. Yad, Tef. III, 18 and Kesef Mishneh a.l.) the reference is to the stitching of the tefillin, and the rules are here stated where two or more stitches had snapped. (21) Or: next to each other, i.e., in adjoining compartments. (22) For it is evident that the leather was of an inferior quality.
The gemoro speaks about the head tefillin when the divisions between the individual scrolls are split.
My chavrusa and I ask: How can you tell when the divisions are split – presumably only when you have opened up the tefilloh?
Do we understand that the difference between old and new tefilloh teaches that there is no inherent problem if the divisions are split - only a problem of hiddur?