@pureblue
That seems very strange that ID # is different in 3750 than the 1350 & 1495.
Is the 9 digit ID number completely different than the 10 digit, or just off by 1 digit?

Why don't you try using the jetmouse KG and generate a unlock key for the 9 digit ID the 3750 displays.
You can rename the working gmapsupp.unl to gmapsupp.txt, then add the newly generated key as gmapsupp.unl.
Try it in the 3750 and see if it works. If it doesn't work, just delete the new unlock file from the SD card and rename the working one back to gmapsupp.unl, that is fastest way to test.

If the card now works in the 3750, I suppose you will need to have another SD card just for that unit.