After learning more about this lost model number matter, I think you should send it to Garmin service.
An alternative is to swap to 34xx firmware and add features like is written in this thread [Only registered and activated users can see links. ]
You have to navigate to get to the good.
[Only registered and activated users can see links. ] Password for my files: gpspower.net Galaxy S5 Kitkat 4.4.2 / Nuvi1200->1250 / Nuvi3790T->34xx / Nuvi 2200 / Nuvi 66 / Oregon 600