My Wambaw is SN M5899C. I got it new when I was a young Jarhead stationed in NC in 1980. I think it had been on the sale rack a couple years so possibly mid 70s manufacture.
The sight window on mine was fairly obviously not cut to center so I recently took a rasp to it and radiused the shelf also. Something is wrong with my string shoulder, can't pull my 55# widow so i'm having fun getting this old 45# to shoot good and quiet.