.662" is nominal for 16ga, but be aware an individual gun may never have been nominal. Many Lefevers in 10 & 12 ga were bored oversize for use by waterfowlers using all brass shells, but I would suspect this is not so prevalent in the 16. I also would suspect the vast majority of 16ga Lefevers had 2 9/16" chambers, but I have a post 1907 16ga H with 28" bbls, both full choked, which has 3" chambers so one never knows until they are measured.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra