IMO, it was made early in the 1920-1930 production run, most likely in 1921.

Mine was made in 1927; and after buying/trying ALL the different vintage slide-action .22's made over the years, have found it to be the best of the bunch (both in quality and accuracy).

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I have one I bought for a song on a package deal with a well used early vintage 10/22. Mine is mid 20s from the serial number. Had a beat up stock, broken in a couple of places, but I actually found a replacement stock from an outfit called Gunville out of NC. Took quite a bit of work to get the rest of the inletting done and I still have to trim down the stock to more factory dimensions, but just happy the way it is for now. This is my deck plinking gun for back yard shooting and, have to say, it is a pure pleasure to shoot with CCI Quiet. The Marlin 38 really is quite a marvel of engineering. They absolutely do not make them like this anymore.

 

I think the D prefix serial number would put it toward the end of production from my understanding. The early guns did not have a letter with the serial number, then they started over again with an 'A' and the last ones had a 'D'. In Brophy's book on Marlins he lists the recorded serial numbers as 782 to 10,938; A206 to A11,389; and D272 to D1,739. Note that your gun is a lower number than was known when the book was written.