Brownings serial numbers and DOBs are sketchy at best for the older guns. Most people quote that C series guns started in 1969 which is true. People then assume that T series guns stopped at that point. This is however not the case. FN/Herstal was notorious for using older parts in newer guns even after "model" changes. They never threw anything away. This is why you will see forged MKIII guns etc...
The T series was actually made up until 1972. I have seen T series guns with serial numbers at high at T378XXX.