I have a WD-45 that came with I think a D-17 seat which was solid and maybe had a cushion on it at one time. I found what I thought was a original WD-45 seat in a Salvage yard with parts of the side lifting option but it has 5 holes in it but the same size as a WD seat. I see the two original WD Allis seats I have only have three holes in them. What Seat do I have with five holes in it and what tractor should it go with?? At the moment that is all I have and really never noticed the difference because I bought one of the Orange-White cushions from a Farm Supply store to dress it up anyway?? Just wondering???Cleddy