I believe that real frame backs are designed with thin blades that can be inserted into a slot in the tang and locked in place with a set screw. That way one razor can accommodate several different blades and the user can replace a dull blade with a sharp one by loosening the screw. You can have a sharpened 7-day set with only a single tang that permits swapping blades in and out.

A faux frameback is similarly constructed, but the blade is welded or soldered in place permanently.

A rattler is a single grind. Here’s a pic of one for sale at Griffiths Shaving Goods.
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