The one on the right is a newer one piece wheel that I have seen retro fitted on m149 water buffalo's and gen set trailers in current use that use the deuce pattern. Observed on many military trains as I live in a major conversion of various railroad lines.
The one on the left I have also seen on some trailers other than m105a3. I think the military is trying to get away from lock rings on the remaining rolling stock with old school deuce pattern.
The bolt holes look different on the ones you have pictured. The first appears to be hub pilot and the second stud pilot. I don't know about their interchangability...but assume it works. Edit....on closer look, the first photo seems to have a bevel, so must be the stud pilot.
There is also a 19.5" (below dual) and 17.5" budd (see A1 above) and for reference a bolster/M1061 rim (16.5") in one piece.
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website like our supporting vendors. Their ads help keep Steel Soldiers going. Please consider disabling your ad blockers for the site. Thanks!