Why is one battery marked #1 on the Voyagers?

[damaltor]

Hi!

I noticed that on Voyager calculators on the backside, there is a diagram showing the three batteries so that the user knows how to insert them. The rightmost battery is marked #1.

As the old Voyagers had two plasic flaps, it is kinda hard to insert this battery first. Also, it should not matter which battery is put in first - so what did I miss, why is the battery marked #1?

Back side of the 11C:
http://www.hpmuseum.org/11cbk.jpg

Malte