# How large is an issar coin in halacha?

The Shulchan Aruch OC (648:2) writes

אתרוג שניקב נקב מפולש כל שהוא פסול ושאינו מפולש אם היה כאיסר פסול ואם חסר כל שהוא פסול ויש אומרים דגם בנקב מפולש בעינן חסרון משהו ושאינו מפולש בחסרון כאיסר - An etrog that has a puncture of any size that goes through its entirety is invalid. If it does not go through but is the size of an issar [coin], it is invalid. If it is missing any amount, it is invalid. Some say that with a puncture that goes through we require some to be missing and with one that does not go through we require it to be missing an issar's worth.

What is the halachic shiur/size of an issar coin nowadays?

Note: The Rambam Shekalim (1:3) poskins

וּמִשְׁקַל הָאִיסָר אַרְבַּע שְׂעוֹרוֹת - the weight of an issar is four barley grains

Although I'm not sure if it's referring to the same coin, Wikipedia says in the section on Biblical coins:

"Issar" (pl. issarim) - a Roman copper coin (As) - 177 mg (2.732 troy grains)

...but I don't know what that measure means today.

• Seemingly this seeks an area not a weight. 177mg could cover any size area depending how thin it is. Jul 1, 2021 at 1:25
• I recall hearing that R Eliashiv paskened on the size of the Issar based on finds of ancient Issar coins, but I couldn't find it after a quick search. It might be on Havdalah rather than on Daled minim. Jul 1, 2021 at 3:21
• See also R Rimon in his sefer/pamphlet on Daled minim (p71) "we aren't expert in the size of an issar" Jul 1, 2021 at 3:30
• Are there any definitions to the shiur of a barley corn in halacha? If so, can we multiply that by four to give the area of an issar?
– NJM
Jul 1, 2021 at 21:21