1 Onza

Reverse

Scale as a centerpiece with the weight as legend around, the purity at the top-left, and the weight in grams at center bottom, and mint under

Script: Latin

Lettering:
UNA ONZA DE PLATA PURA
LEY
.925
PESO
33.625
GRAMOS
Mo

Translation:
One pure silver ounce
Fineness 0.925
Weight 33.625 grams
Mexico Mint

Edge

Reeded

Comment

The coin mint called "de balancín" (of sway), was used in Mexico Mint to make their first coins. This device uses the rotation of a pole on top with weight on a side to get enough speed to force a spiral down and mint the coin (later updated to use steam and then electric motor but the method was the same).

Some people think that these rounds contain more than one troy ounce of silver and are led to believe that they have scored two and a half extra grams of silver for free. The reason that these medallic pieces weigh 33.625 grams (instead of one troy ounce, 31.103 grams) is that the silver alloy used in them is, unusually, only .925 pure. 33.625 grams multiplied by .925 purity = 31.103 grams of pure silver.

Type 3 Reverse:

Price

Date	Mintage	VG	F	VF	XF	AU	UNC
1978 Mo	280000	-	-	-	-	-	-
1979 Mo	4508000	-	-	-	-	-	-
1980 Mo	6104000	-	-	-	-	-	-

Values in the table are based on evaluations by sales realized on Internet platforms. They serve as an indication only for 1 Onza 1978-1980 item.