[B-train Shorty] Kiha 58/28: What's the story with the different roofs?

[Jes]

The B-Train Shorty Kiha 58/28 set comes with two different roofs: Two with and two without (what I assume to be) airconditioning units. See attached pictures.

The box shows a consist of a Kiha 58 with airconditioning and the Kiha 28 without, but on other pictures of the Kiha 58/28 consists found on the net, they appear to both have airconditioning. There's probably an explanation when to use which roof in instructions, but my Japanese isn't that good... So what's the story about this? Have the units been fitted with a/c at a certain moment or is there a more complex explanation?

[disturbman]

I'm not an expert but I think your explanation is correct. Those units must have been retrofited with a/c at a later date. They won't be the first in Japan.

[ToniBabelony]

I thought only KIHA 58's had a/c...

[bikkuri bahn]

The kiha 58 and 28 were retrofitted with aircon from around 1969 (green cars [kiro type] were already fitted).  A diesel engine generator was fitted to the kiha 28, which enabled it to power its own air conditioning as well as a coupled kiha 58 unit.  That's why nowadays you always find kiha58 and kiha28 units in tandem- kiha 58 cannot power its own airconditioning units.

[Jes]

Thanks for the helpful replies.

I guess the Bandai box shows the different types combined to make clear two versions can be build with the kit. A little confusing without the explanation :)