The most early models, had a foam wrap around all sides of the speaker. These would be models like the two way model 1B or 2B, 3 way model 3B or the big 5 driver 3 way, the 4b.
Later on they went to a cloth wrap tape design with a solid wood decorative piece on the rear of the speaker. These had the EX or EXL prefix. I.e EXL2, EXL3 etc.
All the speakers pretty much shared the first-order crossover and mechanical time driver alignment in their design.
Then there was also the big top-of-the-line modesl, the Pendragon and the Excalibar.