An interesting aspect of this older Phillips rod brake bicycle is the use of a rear brake bell crank that threads into the bottom bracket. Phillips advertised these in their catalogs during the Birmingham years going back many decades and into the 1940s-50s. This particular bell crank is a sort of a work of art - heavy, solid metal pieces and that form a bell crank, which then threads into a half-round nut that is inside the bottom bracket.
The internal nut is contoured to match the inside of the bottom bracket and to lock in place - this helps the mechanic to tighten the bell crank into place without having to shove a wrench inside the bottom bracket. It also helps keep a low profile so the nut stays out of the way of the spindle.
Reassembled, we can see the pros and cons of this system, compared to the Raleigh type, which is externally mounted. The Phillips type is very clean in appearance - the bell crank emerges cleanly from the bottom bracket. It also provides a very solid mounting point for the bell crank. However, servicing the system can be a pain - if the bell crank comes loose or you need to access that nut for any reason, you have to go into the bottom bracket. Everything on the Raleigh style can be done externally. But the Phillips style is still a nifty piece of design.