When you swing out the cylinder, it'll be visible on the frame under the piece that holds the barrel.
your colt detective special dates to the year 1949 by the serial number provided.
Are you sure the serial number is correct? The Colt detective special was first produced in 1927 with a starting serial number of 331000,The Colt police positive special from which the Colt detective special was derived from with the serial number 153817 was made in 1918
The Colt detective special was derived from the Colt positive special in 1927and the starting serial number for that year was 331000 so the serial number you show of 3021 does not match up as a Colt detective special. Now if the serial number was 383021 then it was made in 1930.
Colt Detective Special serial number 45418M is within the range 19201M - 59999M which was manufactured in 1977.
Are you sure the detective special serial number started with AE? I do not show a DS starting with 2 letters.
Please check your serial number or model number because the detective special does not show a AE prefix to the serial numbers in my records.