As far as I know and this is based on conversations with Clawson and Meadows, the NRA pistols were chosen at random from pistols in stores at Springfield. The inventory control at Springfield at that time may have been similar to the inventory at a grocery store where they try and sell the oldest items first (First in and first out.) but since the pistols did not go bad as does a head of lettuce, there was no apparent need to control inventory beyond basic stock rotation. None of the history was written down beyond the above magazine clip, as to when the pistol were dispatched to NRA members.
If the pistol program started in 1912 as indicated in the article, a pistol with a 1913 date would have been expected, but if the shipments did not start until later, say 1915 for example, it is still possible that a 1913 pistol which had hung around in the Springfield stores due to lax inventory control became one of the original group. The highest known serial numbers are from 1916 or early 1917 when the country went to war, and the program was terminated. Today we have only a vague idea of how many 1911 pistols were originally marked with the NRA marking. About all we know is that the program started with the "100 pistols" allocation, but since at least 100 NRA pistols have been recorded by collectors, it is likely that that number was increased at some later time. Some good high resolution pictures of the markings would be a big help in determining the authenticity of the marking.