Info on shot gun found at estate

[Gene Fox]

Hello folks great to be a new member! I am looking for some info. I have cruised the internet and could not figure out much about this gun. I even used the Parker site which is very good i must add and still at a road block. I have found this gun at a estate clean out and would like to find out more about it. The patent date is March 26th 1878, and the serial number which is all over the gun is 62070. I have found on the site that this was made in 1890. OK then the frame size is a 3, this is marked exactly where they say to look. Then i go to weight, where they say to look is marked with a 5 (which is large) and a small 7 just to the right of the 5 and a little above. This is where the roadblock starts. i cannot find this number anywhere on the PGCA site. Then going to where the grade is on the water table, it is marked with the serial number and then below this a small N then a patent date of Mar. 16 1875. I just cannot figure this out, i am sure that you guys are a lot smarter than I , and if anyone can help that would be much appreciated. Also there is a butt cover with a dog logo on it seems to be of bakelite. Oh and yes the gun is marked on both sides Parker Bros. I will try and post some photos as soon as i can.
Thanks Gene