Piston Crown Markings

[ss3963]

Pulled the pistons from my 66 Beetle 1300. All four have the size marking of 76.96 stamped on the crown. Three of the four have a small "20" stamped immediately underneath this, and the fourth, an "18". Does anyone know what these additional numbers (18 and 20) are referring to?

[Eric&Barb]

Probably inspection marks. Would help to have a image.

Congrats on your first post!! May there be many more......
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In Stereo, Where Available!

[ss3963]

Here is a photo of the crown markings on one of the pistons stamped with the number 20 below its size marking.

[KTPhil]

Maybe some kind of date code?
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Current Fleet:
- '71 Fastback
- '69 Westfalia
Retired:
- '67 Beetle
- '65 Beetle (x2)
- '65 Bus
- '71 Squareback

[viiking]

Probably a machine or process identifier.

For example most plastic bottles will have a code on the bottom to indicate which mould the bottle was made from. For interest go and have a look at a couple.

When the manufacturing Quality Assurance department identifies that certain bottles are out of specification instead of inspecting multiple machine moulds (multiple tens of them sometimes) they can narrow it down to one machine that is out of specification.

I believe that VW also did that with the case castings for the same reason.

It is modern manufacturing practice to have such identifiers. I assume three of the pistons were made by one machine and one was a different one.
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[Eric&Barb]