According to proofhouse.com, the source for all Colt serial info up to about 1978, 138xxx would be about 1916 or so. However, there is no listing for numbers with a T at the end. Are you sure about the T?
I show it was made in 1917. Condition is everything on these as I bought one about 1 year ago at the big gun show in Louisville for $200 and I would rate it 85 to 90%. they are pretty common guns. Mike
Hey hwcolt, I see you just joined the Forum so welcome!
You've got a great little revolver there. They exhibit outstanding workmanship and are a handy size. I've got one just like yours only a few years older. It shoots tight groups on paper. I like the Police Positives and Police Positive Specials. They seem to just now be getting some of the respect they deserve with prices beginning to rise. Feel free to post a photo so we can have a look at it.