I was in and under the car with a flashlight.  caveat emptor.  I had first dibs from the family. The dad was deceased. I was going to take this mini but I've got 8 other minis and running out of time to complete my existing projects.  Martin, the car was in NY and from NY last registered there.  That German tag is an interesting add on and I'm sure it was done to "increase" interest.  it's a collection of parts needing a donor body.

That sound deadening could have been the glue holding that thing together, along with the spit and Kleenex. The car has almost gone full-Flintstone. If you look at every body piece on that car, it appears that only the roof, bonnet and boot lid are pretty much the only salvageable pieces. Everything else should go in the bin. It's roached everywhere. Lots of panel replacements. And that's just the body. Then there's all of the components of the rest of the car like wiring, plumbing, suspension, etc...pretty much all shot. They have brackets and rivets holding pieces together, and a piece of plywood holding the battery in what's left of the battery box. I don't get what the seller is holding out for. I'd say he's lucky to have a bid of $6199 for it. 

It looks to me that the dynamat- type stuff was used to seal the already rusted out floor.

That stuff on the floor could have been sound deadening mat, aka Dynamat (one brand name for this type of product.) Sound deadening mats like Dynamat are frequently composed of a thin metal sheet bonded to a solid bituminous substance. That substance does melt under high temperatures and could end up looking like tar if neglected.

Whether it was the cause of the rust or a bystander of neglect I can't say. If properly applied, moisture should not be able to get through to the metal, but if poorly applied water can seep into voids of poorly applied mat. (Usually you must at least use a roller-type tool to press and squash the mat down onto the metal.)

I know this car.  It was in storage since the owner passed. Unfortunately the floors were coated with a tar like substance and tin foil applied on top of the "tar" . It's going to need full floors which are perforated with pin holes, aside from the obvious rust shown.  Buyer beware.

No sale. Bid to $6199. https://bringatrailer.com/listing/1965-austin-mini-850/ Wondering what the seller is holding out for. That thing needs a lot of love. Maybe they saw that '64 Cooper'S' Project sell for $26K and thought that they could get close to that, possibly? 

Looks to be an interesting project car. Maybe hailed from Germany judging from the number plate?

Check out the ongoing auction. It looks to be a worthy candidate, and has an apparent 998 dual carb powertrain. Best, MSH