I believe RIA has the less-expensive items grouped in multi-lots in their 'Regional' auction and they reserve the better pieces as individual lots in their 'Premier' auction.
I don't use these type auctions because of the auctioneers' excessive charges, but I have several friends who are frequent participants. We meet once a week for a geezer breakfast to do show-&-tell and talk about everyone else (grin). One of our group is Clarence The Collector, who has been a very frequent auction participant as both buyer and seller and in-person-attendee.
For the last 40 years.
He's on a first-name basis with all the auctioneers and most of their employees, and he is the poster boy for the 'Gun Show Shark' title. I asked him about the auctioneers and their organizations and here's what he said.
"The only honest person I ever knew in the auction business was Terry Dunning and he's retired. He was dead honest but you had to watch his employees."
FWIW Clarence has long been on a first-name basis with such luminaries as George Madis, Larry Wilson and Al Frasca among many others. His auction transactions number in the many, many hundreds if not thousands by now. I tend to believe 90% of what he says but as always YMMV.
Regards, Joe