Ah, you have the old series motors. Diversity Models was kicked to the curb as a Neu distrubutor a long while ago. The current drawings from Neu's site all have 25mm spacing for the 15 series. http://www.neumotors.com/2008/Root/S..._drawings.html
Yes, you got one of the original versions. Same thing happened to me about three years ago, except the drawings had 25mm on them and they were made incorrectly.