[DeTomaso] Secret writing on engine cover wings, paint question

[Clark Family]

The paint has failed on the left and right engine cover panels
on my 73 Pantera so I am stripping and repainting them. Underneath
the paint there is printing on one panel:

    FIA

    Z4

Any clues what this means? I assume manufacturing marks.

It looks acid etched, that survived aircraft paint remover
but the black is fading with rust remover to a dull shadow
of etched steel.

Attached are photos.

The old paint is satin and with a pebbly texture, any ratttlecan
paints that can make the same effect? I ordered a can of textured
under-hood black from Eastwood. What was the central engine cover
originally painted with? Mine looks repainted.

Thanks,
Chris
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