Converting all letters to numbers alphabetical wise. Middle 3 rows all add up the same to 90+45+68 = 203. But 203 isnt prime number. To make it a prime the next prime number is 211. So we are 8 off.

The center square should read 8
or in greek notation Η´

Thanks! Doesn't help me either for now

No. Only the symbols (letters, characters, numbers, etc) in the squares and the arrangement of the symbols matters.

There is one minor clue on the other side of the coin, but no solution offered yet is at the stage where that would be relevant.

Can I ask another hint? Do the grid lines in the background have anything to do with the puzzle, I've been squinting and counting but hoping they're just the artful design.

hi team like what you have said from your PM i'm here to show my interest using your bot. hope you will provide me the copy and i'll give my
honest review in all aspect, good luck and let see how helpful this bot for me.

second attempt:
-portrait engraving

Okay, so here's my answer.

The squares with lines is an anagram for currency
Now for all the other symbols. From left to right, top to bottom:

Chinese symbol upper left is for Nitrogen --> N
h (macron below) --> H
Greek i is for Iota --> I
greek Sigma --> S
Greek Phi --> P
Greek alpha x 2 --> AA
y - 2 is 2 characters before y --> W
C --> C
Greek p is for Rho --> R
Greek Omega --> O
Greek Kappa --> K
Chinese symbol lower right is for Category --> C

So all first letters from those words are:

NHISPAAWCROKC
This is a anagram for CHIP CAN WORK AS

Now put both anagrams together you will have:CHIP CAN WORK AS CURRENCY

The answer is NFC

*fingers crossed*