Nice one RCS, if your rifle bbl and #64145 receiver are original to each other it is then according to the serial number, one of the first rifles as originally assembled off the line in the beginning of 1907. Apparently the arsenal got the approval to begin producing new rifles off the line in 1907 and those are made with all new and the correct dated parts. Prior to 1907, RI rifles are found as being assembled from misc earlier and later made parts were the bbl will not match the serial number date.
I have one like yours having the serial number #87241 originally produced off the line with the correct matching bbl date of 6-07. Ray