I did notice that and also that the bar spring on your spider looks longer and different. So, since the spider doesn't slide into the race bar, then maybe this spider goes with a different machine, not necessarily a Standard.
Your spider may possibly go to another machine. There were some sewing companies that made machines that were able to convert to chain stitching by using a "spider".
This is taken from notes that I had kept from a discussion on another board.
Machines that can convert to chain stitch with attachments:
White Rotaries (not sure if all models convert)(spider & special throat plate)
Domestic VS (spider & special throat plate)
Standard Stout (spider & (not sure but,) maybe special throat plate)
Kenmore several models (spider & special throat plate)
The Standards are pretty machines that have a pretty little hum, like a graceful lady.