Meaning of tag on L6 226

Anyone know what the tag means on top of the head? It has a 1, 20, D.

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It appears to be a casting number, something inserted as part of the manufacturing process for tracking/quality control purposes. However, I've never seen a decoder ring to interpret precisely what they mean.

Thanks Lookout Ranch, appreciate it.


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bmcgrath. I know for sure that it was someones job to change the casting number daily or before the casting run. The one is most likely January, 20th day, 4th year of production for the Super Hurricane engine. I am only guessing and my be wrong. We all know that Willys vehicles may not have sold in the year produced. So they may have kept the year on the date ALPHA coded on the head. It is visable and it may scare off a buyer if it said 57 and your are buying the vehicle in 1959.