14 gauge?

[Jack Hamner]

Hello and THANK YOU for allowing me to join this special forum.
I am not a gun collector per se, but I recently ran across a Parker hammer gun in a local pawn shop and fell in love with it.
I went by the other day and purchased it. It bears a patent date of Nov. 13, 1866, and was advertised as a 14 gauge.
This is evidently true, as I read on another forum about this same gun (serial # N 0968) being sold on an online auction in 2006. A discussion followed about finding ammo for 14 gauges.
I guess what I would like to know is whether or not this gauge is particularly rare in the early Parkers, and also if there is any way of determining the year of production from the serial number. The gun has decarbonized steel barrels (30 1/4 ") and is in good to very good condition.
Thanks in advance for any help you might be able to give me!
P.S.--As I said, I am a novice collector, so please let me know if I have left anything out, and I will try and correct it!