Did Japan print stamps for India in WWII?

Someone I know told me that, during World War II, the Japanese government printed stamps for India–planning to use them there after conquering it. Does anyone know if that’s correct?

And if it is, do stamp collectors consider those stamps valid to trade, put in catalogs, etc.? (Since the stamps were never actually in use–no-one was ever able to use them to send letters.)

I’d never heard of this, but I make no claim to expertise in this area. It seems a weird thing to have done; but, dare I say? – the Japanese can be strange folk.

Philatelists do a great deal of specialising, often about very esoteric stuff: would think it certain that some collectors, anyway, would be eager to acquire and have in their collections, stamps of this description.

You may be referring to the Azad Hind stamps, which were actually printed in Nazi Germany for the Japanese-controlled Indian National Army.

Yes, such cinderella issues are collectible and are listed in some specialized catalogs.