Made in 1951.
418306
1950
You will have to call Colt to find out.
A Colt detective special with that serial # needs a letter either before or after it. Nothing that low before 1970
Colt Detective Special serial numbers do not end in two letters. If you are positive the last two are "RD", you need to call Colt.
Proofhouse.com has Colt sn tables. You can also call Colt and they will tell you.
about 1936 (I believe)
1977.
I believe made about 1913
Was produced in 1960.(750000-776399)
You can look up the sn at Proofhouse.com.
1970