This discussion could actually go on for a while, and would be best if we could get together, hang out and have a nice conversation. Unfortunately, we all live too far apart for that to work, so I'll keep it simple here.
The early no-prefix R9s can be used, but at this point would be better suited for a collector as only roughly 48 were made of those. The reason being as we went along, we were constantly upgrading these pistols. For carry, I would look for something around the R4500 serial numbers up until the last ones we made in the R6000 area for carry as those have all of the upgrades done to them. Others in the R101 to R4500 are also a good choice, but have fewer upgrades than the latter. The none-prefix jobs are more collectable, mostly due to those being the very first ones made and the few numbers produced.
I hope this explanation helps.