Spuddy, the answer is YES, it most certainly is an elevation screw. I have proof and if I can find a particular photo Mike and I took in a small town in upstate New York, you and everyone else will see why I am so sure of this. BTW, Artilleryman is spot on!
I'm searching............Found it! In 2007 Mike and I made a grand tour which included lots of New York State, Vermont, New Hampshire, Maine, and Mass. and Rhode Island. We found the field artillery piece below in Cobleskill, NY on the village green. Sporting this unusual elevation gear, you can see that it was specifically designed for a split trail carriage which indicates 1700s or early 1800s. The cannon on the green or village square is unmarked and about the only thing we know for sure is it's caliber. It's 3.6" with heavy black paint covering everything. A 6 Pdr. Probably early 1800 vintage, but that's only a feeling. A little crude, maybe an independent foundry (small), but the paint and unknown conditions of storage make that only guesswork. Maybe Cannonmn knows more about this one? An article in the Artilleryman magazine indicated this piece is of an unknown maker and the casting date cannot be fixed.
Tracy
Some pics we took in 2007.
Spuddy, does this look familiar?
My hand span dimension is 8", so this should give you a general idea of elevation gear width and breech diameter. Mike and I were walking through Cobleskill looking for a lunch spot when we saw this gun and all our measurement tools were far away in the car.
A 6 pdr. it is. Even with no measuring instruments, we know. The distance from my knuckle to the finger tip on the index finger of my right hand is 3.6-3.7" long. 6 Pdr. bore diameter!
Astragal and fillets and tulip muzzle flair.
Enlarged vent and rough texture can be seen. Matt Switlik would probably know if these carriage irons are authentic.
Sorry about this, but I'm on a nostalgia tour now. This was Lark Street Elementary School where I gazed out the classroom window for hours as the teacher droned on and on in 1st, 2nd and 3rd grade. I looked out that upper, far right window and watched the maple seed twirlers float to the ground. My bean in a water and cotton filled test tube sprouted very nicely.
They were converting my old school to the town Library when we were there. I used to walk up that stairway past Yogy Bear every day back in '55 to get to my third grade classroom. I literally flew down that same stairway every day to go recess!