mattia , thank you.
I'm still learning about magnesium case casting dates . If i'm not mistaken, I see a digit 3 where I have pointed . So that would make it a case cast in the 50th week of 1973 :
Can anyone verify that single digit of the last year of the decade cast were at the right of the bar depression in this casting date on a 1973 / 74 vintage case ? And that in the example provided by mattia above is not just some slag that strangely looks just like a numeral 3 ?? (I would find this hard to believe but one never knows). More from this vintage would need to be examined.
I know by 1977 , this casting date layout had changed . And the last 2 digits of the decade it were cast was below the bar. And I cannot tell for certain , without having one of each physically in front of me. But on mattia's example the circle seems like raised material with the bar and numerals being depressions within the raised circle. In the example below , it seems (to me) to be the opposite.....that the circle is a depression & that the numerals & bar are raised material within the depression.
Here is an example from 1979.
Thx again mattia. Now back to your case. I would not be so quick to discount your case as being anything one way or another until you study it harder. Way too many people are quick to discount things as 'phony' just because they are differant than the norm. One does not always mean the other.
I do not know anything for certain . But a few questions go off in my mind. First , why would someone do the unit number so strangely if they were trying to fool anyone ? And if stamped over a complete other existing unit number , why does the surface not look like it has been ground ?
Lastly I have seen all the digit stamps on your unit number (664 0308) used by the factory before. Even if I said the were not the 'normal' ones used for that location / that year. I did not mean they were fonts that were never used
Again, I would break out some high powered magnifying instrument , and examine things very closely. Is that actually a star under the 8 ? Is it an 8 and not a 3 (is either ...the number that records show , was originally put in your chassis ?).
Is there any reason to think that your car was special in some way. Motors and chassis that were built away from the normal production areas sometime have strange stampings that can have font digits normally used in other model years & other stamping locations/applications.
I am not saying this is the case , just that I would study it closely before I made up my mind conclusively.