Well, I finally saw this and it is a topic I really like. Been preoccupied with my own upcoming march south....in peace.
I am fortunate enough to have both the 4.62 shell and the 6.4 bolt, with the 4.62 more of my liking in condition. I bought the 4.62 at Mansfield in 2014 and the 6.4 at Mansfield in 2015. I am not sure which is actually scarcer, but had seen a 4.62 previous, but not a 6.4.
However, I am certain the 2.6" Bolt for the Wiard Rifle is the scarcest of my James Gang. The last figure I heard (2013) there were 5 of them known.