I have finished my research on these now.
I've got a 1.75 pair and a 1.85 pair and I conclude the following :
a) the 1.75 pair look betterer on my Sport but having been running 1.95 Primo's look a bit thin to be riding... so I'm running the 1.85s
b) the 1.75s have a blue Oddy logo and the 1.85s have a orange logo
c) the 1.75 have a 'crucifix' tread but the top of the crucifix is offset... the 1.85 have a 'crucifix' tread and its not offset.
Conclusion - I like these tyres.