Great find, Steve. I'm the owner of SN 30041 that Stephen referred to. He and I have a very friendly competition over finding these early guns. The trunion you refer to is what we call a rotary check joint that was used on all of the Syracuse guns beginning c. 1885 thru 1899 to about SN 73,000. The "marks" that you refer to on the underside of the barrels may be XX or XXX. If so your gun definitely deserves a research letter. Post photos if you can or send the photos to cedarclyffelodge@gmail.com and I'll post them for you