Centuries ago, when dishonest potters would try to pass off their cracked pots and jars as high quality, they would fill the fractures with wax and then smooth it all over so their customers couldn’t see the defects.

Gullible buyers wouldn’t notice the cracks until they poured hot water into the jars; they would leak right away. Savvy buyers in the marketplace would examine the jar cracks by lifting it to the sun, literally “sun-judging” it.

Sincere is the transliteration of the Latin phrase sine (without) cera (wax). Honest sellers invited their wares to be sun-judged.--- Author Unknown