I'm glad you guys got to see it in person. Pretty cool jacket! When we were walking into the meeting room to look at it, from a distance my first impression was that it was a NY state jacket. As exciting as that would have been, I was pretty excited when it wasn't. The little details got me going like the sack coat cuffs you mentioned. Did you notice that the cuffs once had small buttons attached, but are now missing?
I'm still not sure what to make of the stylistic similarities it has in common with NY state jackets. My pet theory is that perhaps the firm that produced the Spaulding jacket had a NY jacket to compare it to...something like the "sealed pattern" uniforms at Schuylkill Arsenal. Maybe the local manufacturers retained some features out of functionality but cut back on the superfluous stuff like trim, exterior pocket, and the NY style chest linings that would generate a lot of hand-sewing. The way the jacket is constructed also seems to hint at a streamlined mass-production technique, i.e. the interior machine and hand sewing is in brown thread, topstitching is black thread, and the buttonholes are black silk. I can see a building full of people cranking these things out through piece work.