When you open up the cylinder,it should be located inside on the frame at the swivel.
If your Colt official police is chambered in .22cal?Then it was made in 1937.
your colt official police was made in 1958.
Made in 1929.
50-500 usd
Colt official police with serial # 904734 was produced around 1965
1940
1929
1967
Around 1943.
Manufactured in 1950
made about 1958
$400