You are right, but you are wrong too...
Indeed on the original picture the car has a plate "2300 S". But for a reason I don't know, this was a 2500 SS.
The proof is that in the same catalogue they also pictured the 2 different coupes: the 2300 S coupé kept the original disk wheels, while the 2500 SS was fitted with those wonderful Rudge Special.
But they only had one cabriolet (it's clear in the cover picture, with the full line-up) and - hard to understand- they put the "2300 S" plate on what was actually a 2500 SS, and used the same car for both the descriptions inside the brochure.