67 68 brake rotor casting numbers

[Rsconv68]

Specifically asking about the 2 piece brake rotor “hat”, I’ve searched and have not found any threads with pictures of the casting numbers on the inside/underside. I’ve read a few posts but sometimes the cast and part number do not align. I’ve got one cooking in the electrolysis vat and am hoping to identify as correct/original. Any help with both sets of numbers and pictures is very much appreciated, or a link.
Thanks in advance

[X66 714]

I have 5 undersize rotor hats & only one has a casting number. that one was 3910881...Joe

[Jonesy]

If I recall correctly my original rotors had a yellow ink stamping on them with 3 numbers indicating day of the year they were made. But no casting numbers.

[daveg]

this is on both sides.

[Rsconv68]

Here’s what it has. I’m hoping someone has a comparable photo to help out. Rusted …yea.

[daveg]

Back of rotor with yellow mark above.
Not rusted, just poor casting.
Note grey areas.

Yours looks to have been beat on some.