I actually own one of the stingers in .22lr; useless as anything other than a "conversation piece". It was made in the Soo; they are no longer in business. When I brought it in during the days of the Michigan "pistol inspection", the clerk thought it was the most interesting thing she had ever seen. About 4-5 Police Officers came in and took a look at it.
Like Michigander said, it was not an AOW, I believe because one needed to actually fold it to shoot. Then to reload, unscrew the end, pull out the spent casing and insert another .22lr cartridge and screw it back on. The safety was a slide, but it always seemed to be moving around and I thought it was pretty unsafe.
It is not illegal to make a firearm per se, but making a functional firearm that looks like something else is risky (especially a .357 :what, but it can be done. In my "not so distant" past I made a homemade 9mm pistol and I made a shotgun. As long as you register after you make it, I don't see what the problem would be. Perhaps someone here knows better than I do regarding the legalities??