Spinner "backplate" vs spinner "bulkhead" (?)

[Canuck]

For a fixed-pitch propeller on a PA-28, what is the difference between a spinner "backplate" and a spinner "bulkhead"?

The Piper PA-28-161 service manual seems to use the two interchangeably. The PA-28-161 parts manual lists a "backplate" up to the 1978 model year, then a "bulkhead" from 1979 on, both with the same illustration in the exploded diagram.

Is it just a shift in terminology, or are they actually different in some way (other than the number/location of screw holes to attach the spinner)?

Thanks! I'm asking, because the shop has discovered a crack in mine, and I'm always interested to learn more about my plane.

 

[reb]

 

[rwyerosk]

 

[magman]

 

[cappy48]

 

[kshaw]

 

[rwyerosk]

 

[cappy48]

 

[Canuck]

 

[rwyerosk]