Made in 1935.
Rummaging in the safe tonight, I came across a COP 4", marked as such on the bbl, serial # suggests mfg in 1954 with number in the middle of the Marshal range, Yet this OP had a ROUND butt and NO "M" prefix on the serial #. There is an additional 5 digit number stamped on the rear grip strap like a department inventory #. I love a mysterious oddity.