HelloBelfrybat,

Everyone is right in saying that a Singer 15 (any 15) is too big for a cabinet for a 99. The length and breadth of the base of a 15 are larger and the hinges are further apart. The 15 will not fit in a cabinet made for a 99.

The reason that there is a gap to the right of the 99 in the cabinet is that this is the space that would accommodate the treadle belt - but there is no belt because it has a motor.

My 99 has a hook in the lower right which is part of winding the bobbin process. Mine is also electric... I don't see a bobbin winder on this one either? :/ I was just seeing on my 99 yesterday. Though this does look shorter. I'm confused really.