Interesting discovery made today regarding key blanks. Mark (914Sixer) re-keyed a complete lockset for my '73 recently using misc parts. With the set, he gave me a nice ilco key blank (PO5-P) with plastic grip... similar to the red and black Porsche keys that are all over eBay.
I took the blank to my locksmith and had it cut, to match the original. When I tried it, I discovered that it would turn perfectly fine clockwise, but was really difficult to turn counter clockwise... in every lock except one... the driver's door handle.
The locksmith couldn't figure it out, so I took the set home and continued to fiddle... I dissected a few locks and found the cuts to be true. Then I discovered that the passenger door tumbler was different from the driver's side...
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So then I looked at the keys closer and discovered another difference...
Click to view attachment
I discovered that the extra "ridge" on the Good key is required to turn the tumbler counter clockwise. Without it, the key presses the wafers outward when turning counterclockwise, which causes them to bind in the cylinder.
Apparently, the only lock where this wasn't the case, was the driver's door lock... the one with the slot cut around the neck.
So I'm off the order a proper key blank...