There were over 550,000 of the 38 DA made and over 200,000 of the 4th Model manufactured so there are plenty of all barrel lengths made. The SWCA database shows the following:

Barrel . . . 4th Model . . . All Models
3.25". . . . . 32% . . . . . . . . . .56%
4". . . . . . . 20% . . . . . . . . . . 11%
5". . . . . . . 32% . . . . . . . . . . 14%
6". . . . . . . 16% . . . . . . . . . . 10%

There is a margin of error in this kind of comparison, but it gives you an approximation that should suffice as about the only method available to give that estimate. You will also find no mention of any premiums paid for a particular barrel length in Supica's book for any of the 38 DA models. One interesting observation is that buyers preferences changed over time. The early years of production saw a big preference for 3.25" guns.

There are also 2", 8", and 10" examples known, but I do not know how many were officially lettered.

__________________
Gary
SWCA 2515