I picked up a S&W 64-1

*The serial: 1D131
*Stamped on the LEFT side frame: WSPD 555
*It is: SS, a 4" barrel, marked 38 S&W SPECIAL CTG

The number inside the crane `6872 and another series of double stamped letters matches the numbers/letters stamped on the fame location.

I am thinking this is not messed with other than the trigger is super lite, which was probably lightened up a bit.

I did a check on google and ran WSPD; I came up with Winston Salem Police Department. I think it is in North Carolina. They said if I recall, they have 594 positions. I wonder if the 555 was a badge number? I was told it was.

I did run the Serial number `1D131 and the crane number on the stolen guns list and came back negative. So this is not a stolen gun.

I have spent better than 2 hours reading old posts on the 64-1 listed here. In the 36 plus pages I went through I found only 1 ref to a 1D6 and another 1D1 111 and a 1D 2xx. The question I have is:

What was the earliest serial of the 1D serials for the 64-1, guessing 1? If 1D was the start of the serial, then is #131 produced on day 1 or 2 or 3; depending how many guns were produced each day?

Was #131 a prototype of the 64-1 series? At what number did the prototypes stop?

I am trying to understand what the heck I just purchased. I thought the serial 131 seemed low if you consider 1D as a starting point. I had not read any of the forum information prior to the purchase of the pistol. I was impressed to purchase it as it was a "PD" marked gun stamped and the trigger pull in SA was almost like 1-3 lbs. Very very light pull.