59AB Head Difference?

[51woodie]

I noticed that the cylinder heads on the 59AB in my '46 Coupe have different numbers on them. Some cast in and some look like they were stamped in. Is this normal during production, or has one of the heads been replaced? This was originally a California car, and I believe I am the sixth owner. This is just a question out of curiosity.
The left (driver's side) has 59A-B cast in, and the number 13 stamped below the Ford logo.
The right (pass side) has 59AB cast in, and USA and the number 2 stamped below the Ford logo.

 

[FritzJr]

There is no way of knowing what the other 5 owners may have done to the engine, but the stamped numbers do not any known meaning. If both heads are have the 59AB cast in, they are likely to be quite similar to one another, but maybe not original to the engine.

 

[rotorwrench]

Ford started with the 59A heads in 1945 and made a small change to get the 59AB heads sometime in 1946. They continued making them at Ford through 1948. There may have been subcontractors casting them after that for a few years as spare parts. They are likely to have variations due to that amount of time in production.