Somebody pull a rabbit out of their hat. I have searched VIN listings and cannot find the one I just acquired.
DT1F-103222

I see what you mean . It's almost certainly a 72 DT2 , but perhaps originated from another market .
Possibly a Japanese Domestic Market bike . We have had instances of servicemen bringing home bikes before .
A photo might help this too .

If you want answers from the VIN experts they'll want to see clear pictures of the engine and frame VIN stampings...

Here are photos each side along with both numbers

posted photos

Hopefully DEET or Enduronut will weigh in...

There was another thread on here where DEET identified that it looked like an extra "1" was squeezed in after the dash on the frame number... and I believe I remember reading that the number on the case the font size should be the same for whole number, not smaller font after the dash.

As was mentioned yours could be an original JDM bike or something else unusual and unique though! I just don't know enough about that model to be sure.

VIN number aside... it looks like a really nice bike with maybe a GYT pipe.

Color scheme and VIN style match my once mandarin orange '72 Dt250, which is DT1F-116749 (according to the vin link on the site it should have been pearl yellow)
www.yamaha-enduros.com/index.php/forums/...eable-parts-question

Studying the numbers, . . . yes . . . the number "1" appears to be added to the frame number.

The engine case could be a replacement case which comes un-stamped from the factory . . . except for the prefix DT1F 

What I believe you have is . . . a fairly rare version of the 71 DT1E Enduro model
Yours appears to have the close ratio transmission . . . only 3,392 such bikes were made.

Someone may have added the mx engine parts . . . . or . . . someone may have installed another engine all together ... meaning maybe the close ratio tranny isn't even there anymore.
A couple of ways to tell if that's still the original engine or not, is to either compare the countershaft rotations to the engine rotations while in the different gears . . .or,
take the engine apart and count the teeth on the different gears and compare that to the normal Enduro model tooth count.

Are there any numbers stamped into the top edge of the carburetor's mounting flange?

Amendment NOTE:  After further review, it appears Yamaha went with a smaller numerical font in their 1971 serial numbers, so . . .  this 71 (and later models) ARE legitimate Yamaha stampings! 
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Hey EN,
if you got a frame from Yamaha would there be a vin number or blank.

Curious what your translation on this one would be?