Can you weigh it? I always heard that couldn't happen because if the reverse die isn't there then the obverse die has nothing to press the blank planchet against, therefore no obverse image would appear.
There is one possibility, if 2 coin blanks go into the machine at the same time and are struck together. One would get the obverse image and the other would get the reverse image. But, I don't know if the 2 coins would be fused together that way or not.
Two coins can go into the press at the same time and strike this way, that is called a Uniface Strike. A good way to know if they're authentic is they will have very strong strikes and some finning of the rims. And of coarse they need to be weighed. Authentic uniface strikes have a nice premium. CU cents ave. $20-$35, or whatever someone is willing to pay. I know my earlier post said it was impossible, but I was thinking of something else. Plus I wasn't awake:)