In my records I have hammer guns in the 25xxx serial number range with no makers name on barrels. One of the last ones with L.C. Smith Maker is 26397 c.1889. These all have the squared lug going through the receiver. Serial number 26644 has the round lug no barrel markings and the flat side plate connecting screw.
Hunter Arms Co. started in 1889 with the machinery and personnel being moved to Fulton along with partly assembled hammer guns and parts, these guns had no makers name on barrels.
Interesting was that there were no hammerless guns made. The last hammerless gun that I have is 23553. There were no guns made in the 24000 range and 25229 is the earliest Fulton hammer gun I have.