When you take a census of the Israelite people according to their being counted, each shall pay Hashem a ransom for himself on being counted, that no plague may come upon them through their being counted.
זה יתנו. הֶרְאָה לוֹ כְּמִין מַטְבֵּעַ שֶׁל אֵשׁ וּמִשְׁקָלָהּ מַחֲצִית הַשֶּׁקֶל וְאוֹמֵר לוֹ כָּזֶה יִתְּנוּ (תלמוד ירושלמי שק' א'):
זה יתנו THIS SHALL THEY GIVE — He (God) showed him (Moses) a kind of fiery coin the weight of which was half a shekel and said to him, “Like this [zeh] shall they give” (Midrash Tanchuma, Ki Tisa 9).
אמר רבי מאיר כמין מטבע של אש הוציא הקב"ה מתחת כסא כבודו והראהו למשה ואמר לו זה יתנו כזה יתנו:
Rabbi Meir said: The Holy One, blessed be He, removed from beneath His throne of glory a coin of fire and showed it to Moses. Then He said to him: This they shall give.
What is so complicated about a coin, that G-d had to show Moses what it looked like?
The Talmud & Midrash note other things that Moses did not know about (such as how to make the Menorah; how to sanctify the new moon; which insect would render one ritually impure; and others).
Additionally, how does seeing a coin made out of fire help one make an actual half-shekel coin?
† טָבַע vb. sink, sink down (NH id.; Aramaic ܛܒܰܥ, טְבַע; Ph. טבע coin; Assyrian ṭebû, sink in, ṭabbîʾu, diver (water-fowl) etc., v. Muss-ArnoltJBL xi, 1892, 170 DlHWB; Arabic طَبَعَ seal, stamp, imprint; Ethiopic ጠምዐ dip)—
Qal Pf. טָבַעְתִּי ψ 69:3; טָֽבְעוּ ψ 9:16 La 2:9; Impf. וַיִּטְבַּע Je 38:6; וַתִּטְבַּע 1 S 17:49; אֶטְבָּ֑עָה ψ 69:15;—sink, sink down, intrans., c. בְּ; 1 S 17:49 (stone into Goliath’s forehead); Je 38:6 (Jerem. in mire of dungeon); La 2:9 (gates of Jerus. into ground); metaph. of distress; ψ 69:3 ט׳בִיוֵן מְצוּלָה; 69:15 (‖ הצילני מִטִּיט); nations into the pit (בַּשַּׁחַת) 9:16.
Pu. Pf. טֻבְּעוּ be sunk Ex 15:4 (poem) of Egyptians drowned בְּיַם־סוּף.
Hoph. Pf. הָטְבְּעוּ be sunk בַבֹּץ in the mire, of feet, metaph. of entanglements and difficulties Je 38:22; הָטְבָּ֑עוּ, of pedestals (אֲדָנִים) of the earth, as settled, planted עַל Jb 38:6 (‖ ירה פִּנָּה); abs. of mountains Pr 8:25.
טַבַּ֫עַת n.f. signet, signet-ring, ring (on format. v. LagBN 88; Assyrian ṭimbu’u, seal-ring, Muss-Arnoltl.c.)—abs. טַבַּעַת Ex 26:24 + 3 times; cstr. id. Est 3:12 + 3 times; טַבַּעְתּוֹ Gn 41:42 + 2 times; pl. abs. טַבָּעוֹת Is 3:21 Ex 28:23; טַבָּעֹת Ex 25:12(×2) + 14 times; cstr. טַבְּעוֹת Ex 28:23 + 2 times; טַבְּעֹת Ex 25:12 + 12 times; sf. טַבְּעֹתָ֯ו Ex 28:28; 39:21; טַבְּעֹתֵיהֶם Ex 26:29; טַבְּעֹתָם 36:34;—
creating it in the image of God—
creating them male and female.
לְפִיכָךְ נִבְרָא אָדָם יְחִידִי, לְלַמֶּדְךָ, שֶׁכָּל הַמְאַבֵּד נֶפֶשׁ אַחַת מִיִּשְׂרָאֵל, מַעֲלֶה עָלָיו הַכָּתוּב כְּאִלּוּ אִבֵּד עוֹלָם מָלֵא. וְכָל הַמְקַיֵּם נֶפֶשׁ אַחַת מִיִּשְׂרָאֵל, מַעֲלֶה עָלָיו הַכָּתוּב כְּאִלּוּ קִיֵּם עוֹלָם מָלֵא. וּמִפְּנֵי שְׁלוֹם הַבְּרִיּוֹת, שֶׁלֹּא יֹאמַר אָדָם לַחֲבֵרוֹ אַבָּא גָדוֹל מֵאָבִיךָ. וְשֶׁלֹּא יְהוּ מִינִין אוֹמְרִים, הַרְבֵּה רָשֻׁיּוֹת בַּשָּׁמָיִם. וּלְהַגִּיד גְּדֻלָּתוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא, שֶׁאָדָם טוֹבֵעַ כַּמָּה מַטְבְּעוֹת בְּחוֹתָם אֶחָד וְכֻלָּן דּוֹמִין זֶה לָזֶה, וּמֶלֶךְ מַלְכֵי הַמְּלָכִים הַקָּדוֹשׁ בָּרוּךְ הוּא טָבַע כָּל אָדָם בְּחוֹתָמוֹ שֶׁל אָדָם הָרִאשׁוֹן וְאֵין אֶחָד מֵהֶן דּוֹמֶה לַחֲבֵרוֹ. לְפִיכָךְ כָּל אֶחָד וְאֶחָד חַיָּב לוֹמַר, בִּשְׁבִילִי נִבְרָא הָעוֹלָם. :
Therefore, Adam the first man was created alone, to teach you that with regard to anyone who destroys one soul from the Jewish people, i.e., kills one Jew, the verse ascribes him blame as if he destroyed an entire world, as Adam was one person, from whom the population of an entire world came forth. And conversely, anyone who sustains one soul from the Jewish people, the verse ascribes him credit as if he sustained an entire world. The mishna cites another reason Adam the first man was created alone: And this was done due to the importance of maintaining peace among people, so that one person will not say to another: My father, i.e., progenitor, is greater than your father. And it was also so that the heretics who believe in multiple gods will not say: There are many authorities in Heaven, and each created a different person.
And this serves to tell of the greatness of the Holy One, Blessed be He, as when a person stamps several coins with one seal, they are all similar to each other. But the supreme King of kings, the Holy One, Blessed be He, stamped all people with the seal of Adam the first man, as all of them are his offspring, and not one of them is similar to another.
Therefore, since all humanity descends from one person, each and every person is obligated to say: The world was created for me, as one person can be the source of all humanity, and recognize the significance of his actions.