Congratulations
Proofhouse.com has Colt sn data.
A serial number is needed to answer the question.
about 1883
1877
1919
Impossible to answer without the serial number. If you call Colt with the sn, they will tell you.
about 1907
1921
That sn does not follow normal convention for the range Cobra's are in. Recommend you call Colt.
made about 1929
That seems about right.
Need the exact model to answer.