There are no other marks in front of the trigger, there are Nitro stamped on each barrel, with an eagle proof.
I had the chambers measured and was told they are 2 3/4", so I will have that double checked. My uncle use to duck hunt with this gun, and I have used it for dove, quail, pheasant, and sporting clays. It is a nice bird gun, and it has a nice length of pull. My uncle was well over 6', and I am 6'3", and it fits me like a glove. I won't shoot it again until I have the chambers checked once more.
Is there a list of what the proof marks mean somewhere?