Different types of synchro cone design?

I have two JH gearboxes apart right now and noticed that they have different synchro designs. They are both off XK120s. I see no mention of this design change in the parts book or the shop manual. I wonder if anyone has come across this before? The one on the left must be an earlier design, the one on the right is what i typically see in JH and JL boxes. $.02 and speculations welcome.