XK120 leaf springs with 8 leaves?

I recently started with the restauration of my XK120 FHC (S680764, built Feb '53). Now I have the first question and hope that it will be answered in this very competent forum: The two leaf springs on the rear axle consist of eight leaves each instead of seven as to my knowledge should. On the smallest leaf is stamped ‘C4893’, ‘1-6-51’ and ‘3’. According to Bernard Viart’s book it was possible to order XK120 with so called ‘Alpine’ eight leaves springs but with the same part number as seven leaves, C5721. Are the eight leaf springs C4893 the right ones for the car?
Regards Joerg

C.4893 is the part number for the leaf spring on an early Mark VII.
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You may have a case of mix-n-match amateur competition springing.
Mine also had some odd sized leaves when it came to me.
Better measure all the leaves, width, length and thickness.
List them here.
A few of us have gone through this and can help figure out what you have and what doesn’t belong.

Thank you Rob for your clear explanation. Your assumption about the reason for that is probably true. At the moment I’m dismanteling the chassis which I want to restore first. After that I will come back to the leaf springs.
Regards Joerg