I'm not sure what 1898 was using but wasn't it a lucky 7 type with a bolt on top? His seat stays are different than the pic. Hmmm ...
Yes Corbettclassics, in 1898 National appears to still be using the seat binder bolt. Your National is actually one of the early collet seat binder frame designs 1899 or later because it still has the boss. DonC3's bike frame is later than yours 1904 or later according to the catalogs since it has no frame boss.
If the catalog illustrations (photo below) are to be believed. The frame boss you see on your bike and in the catalog artwork for 1899-1902 shows the intermediate design which I believe is a carryover from the earlier binder bolt frames. The 1903 catalog unfortunately does not include an illustration of the seat binder so I'm not confidant when the transition took place. However the 1904 catalog does shows the new artwork with boss being eliminated. The artwork showing boss eliminated remained in catalogs all the way up to the end 1916.
So if the catalog artwork is to be believed and we temporally ignore DonC3's crank sprocket, DonC3's National "frame" could have been manufactured anywhere between 1904 to 1916. The components (handle bars, stem, seat, pedals) on DonC3's National are all shown in 1913-1916 catalogs. And again, according to the catalogs, the crank on DonC3's National appeared in the catalogs anywhere between 1898-1900 and possibly later but simply not illustrated in catalogs.
DonC3's National leads to alot of confusion because it doesn't align with any particular year of National production but has parts from all different time periods. Reminds me of a Johnny Cash song "one piece at a time" as it appears that DonC3's National is built from a variety of parts.
The only thing that could really help date DonC3's National at this point is the serial number. The serial number would be the best evidence of when DonC3's National was manufactured.