Definitely not "A" class - they're much bigger & average 54" - 58" (137cm - 147cm) waterline length.
My guess is it's not a commercial yacht but something homemade. It's almost identical in length, & has a similar keel, to the yachts "Comet" BR4 & "Baltic Star" SB4 produced by the Star Yacht Company, Birkenhead, England, although they're slightly beamier at 18.5 cm.
I've attached a couple of images of both that might give you an idea for a sail plan.
Hope this helps
Mark.