from an online PDF and at Jacks 0206-624 if it is a SV24B. A facebook post in a Yazoo forum someone said they get theirs custom made because they are slotted. One Yazoo blade for another had a rectangular hole. Might have to change the blade mount to use common blades.
Here is a photo of a Yazoo blade adapter from online. Does it look like this or are we in for some spam soon?
I had a 76" Yazoo HPTOK that had that blade adapter. They are prone to breaking and i had to make my own as i could not find any on the web. Yazoo made lots of left hand discharge mowers so they need left hand blades.