I think your gun is a superposed, built in 1967.
"From 1962 serial numbers were followed by the date of manufacture.
2S=12 gauge for the year 1962.
2V=20 gauge for the year 1962.
2F=28 gauge for the year 1962.
2J=.410 bore for the year 1962.
Example: 6556S2 = A 1962 Superposed 12 ga. shotgun with serial number 6556."
I think the above wording is somewhat confusing. Your serial number is "S7" which would mean 12 gauge, 1967 manufacture.