In a type 110 camera of the pocket type from a major german brand, but made in Japan, I found a battery I never came across in my many cameras:
4.5V type K
I even do not remember to have come across this battery, in a shop back then. The seller was a major post-order company, so obtaining a spare battery via mail should not have been irritant to the buyer.
Bu still, why got a general consumer camera such a battery?
Google '4.5V type K battery' for more information. It seems they were used in Kodak 110 cameras and sold by Kodak.
I don't doubt that (my battery sample is from Ucar), but why selling a camera in a region where that battery is rare item? (At least to my memory; I shall look into accessories/wholesaler catalogs of that time.)
That type K is nearly the size of two AAA batteries, though yielding a higher voltage.
(To be fair: I could do a exhibition on photo-batteries alone. There had been too much types.)
It's a case with 3 PX-625 sized batteries arranged diagonally and joined (like knocked-over dominoes).
I've had some luck cracking the cases and making my own replacements. But it is a hard-to-find battery. They were mercury cells originally.