Sorry about deleting the OP, but after I posted it, and I thought before anyone had replied, I did a search and found philips head screws were not invented until the 30/s, so they could not be original on a 28, as all of you have said.
It was just the fit and finish of the screws in the post and the originality of the rest of the car led me astray.
After all, a local model A owner told me my robertson screws in dash panel were wrong too, so is always best to ask before removing something and damaging it , IF it is original.
If it is not original, it don/t matter, chop it out, like I did with the plastic wiring fitted.
Dave, my car has wood "stringers", are they the main longitudinal body bearers that sit on chassis and bolt thru valance.
The whole lower frame/floor is wood, including a drop down shallow tool/junk chest with a pull ring lift up lid set into the rear floor.
While on the subject of under floor, what held the rear wiring to chassis after it passed thru chassis gap at brake cross shaft and went to rear?
It must need some sort of clip to stop it falling on the muffler?
I presume LHD cars have wiring going down the left opposite side to muffler.