Very interesting gun, to call this a Syracuse gun made in Fulton, I don't believe so. It has all the attributes of a Syracuse gun except I have never seen a Syracuse gun with slanted breech balls, they were all rounded. The barrel steel looks correct for Syracuse and unfinished barrels of this type were probably sent with other parts to Fulton in late 1889. The serial number is too high for a Syracuse gun which stopped at around 23,553 from my records which has on the center rib L.C. Smith Maker, Syracuse, N.Y. Guns after this have no maker's name on barrels. The nautilus style of lock plate engraving was a Syracuse thing and carried over in the beginning of Fulton. Yours has the large convex ribs which Fulton later made them more narrow and finally stopped. I don't know when because I haven't followed the early Fulton guns.
Does your for-end tip have the hour-glass shaped ebony tip or the diamond? Syracuse guns all had the hour-glass ones.
Fulton made like Syracuse guns started using Stub Twist barrels for Quality 2 guns, which Syracuse did not, they used what they called Good Damascus in their catalogs.