Marlin 1893 serial number confusion

[fenris]

I recently purchased an 1893,, but when I looked for a manufacture date I get a confusing result. Serial D339
it is a round barrel, full length mag tube with a case hardened receiver White metal front site, Buckhorn rear site No proof marks seen
Barrel marked-Marlin Firearms Co, New Haven, pat.#s 1887,1889, 1893, Special Smokeless Steel, 30 30
Receiver is Marlin Safety, and is drilled /tapped presumably for a peep sight
Upper tang has "Model 1893
When I plug in the serial number, it comes back as pre-1883. Hence the confusion.
Anyone have any thoughts?
Thanks!

[Regnier (gunrunner)]

Fenris;

Is that serial number located up near the forearm?

[Prairie Buck]

Even Brophy indicates he is confused. Page 204 of his book, he says, " To add to the number-game confusion, the model designation was changed from Model 1893 to Model '93, Some of the '93 serial numbers included B, C, and D prefixes that are found on the trigger plate or lower tang." Is there anything on the left side of the upper tang, only visible when the stock is off.