Check this out.

I'm getting my car soon. I understand the engine is original and I'm trying not to pester the seller, so I decided to figure out what engine-serial number I should expect to see when I get the car.

So I went to the registry. I found cars made before, and after my cars VIN and the owners listed their engine numbers. (Bless them!).

But here's the thing: The engine number for the car made before mine ended with #38664. The engine number for the car made after mine ended with #38336. Both owners believe these to be original engines, and it makes sense they would be original since the numbers are so close together.

So unless the fine folks at Porsche were numbering engines backwards, they weren't exactly putting the engines in the cars in numerical order. Perhaps they were made in batches, or during assembly were just pulled off of a pallet.

So it may not be feasible to dead reckon an engine number for your VIN.

Mclovin

correct

same for transmission numbers and Karmann body numbers ...

It can get worse than that. My engine should have been in a car up to 4 months earlier. It must have been sitting around. When I took it apart the one head gasket was folded over, so I wondered if they had set it aside so long that they forgot why. Same thing with all Porsche. Consider the first 911 off of the line VIN #7, engine #57 & transmission #89.

Both VW and porsche are known for using up old stock, workers taking from the middle of the pile, not recording numbers, etc.
To me numbers matching is guesstimate.
That's why Porsche wants you to give them your engine number for a COA, if it sounds about right that's what they will put down.

I bet a cheat could get any case number made the same week as the car and shoot that in with a COA app, as long as they have no record of it and it sounds about right they will give you the COA.
Voila! numbers matching car.

I bet this has already been done by a few of the usual suspects.