I can't make out any detail with the beams or the daggerboards - but it looks like a Prindle 18-2 or a Prindle 19...except that I don't recall them having bridel tangs onthe outsides of the hulls (Doesn't the Dart 18 have skegs instead of boards?)
http://www.performancecat.com/prindle/pdffiles/Prindle18-2.pdfhttp://www.performancecat.com/prindle/pdffiles/Prindle19.pdf 
