32 ga was/is a legitimate shotshell, seems to have been somewhat popular for "garden" or "rook" guns back aways. I've seen a couple H&R older model shotguns chambered for the 32. I've also seen several of the tranquilizer guns that Tim mentions above. Most, maybe all, were produced for a company, name escapes me right now, that put out a kit called the "Cap - sure" (
) system - dart guns. These show up on the on-line auction sites, a couple times a year. I believe there is a bore restriction which inhibits or denies the use of shotshells.
32 ga is not equivalent to the .410 bore which bores out to a 69 ga, IIRC.