100-1000 USD + depending on specifics.
The Colt DA 38 Model # 1901, can only use a 38 short, not a long or special.
No way to value without a detailed description
Impossible to value with just the sn.
The value can vary widely based on condition and age. A Colt DA 38 can sell anywhere between $300-1,000.
Only Colt knows
Yes.
You could get a historical letter from Colt. Cost is about 100 USD or so.
DA 38 Seril # Army 138 501
What model?
A type of DA revolver made by Colt.
10-1000 USD depending on EXACTLY what you have, its condition, box, papers, accessories.
Jerry Kuhnausen has published the book you need.