What does -575 mean on gold hallmark is it gold plated?

.999 = 24 carat = 99.9%

.916 = 22 carat = 91.6%

.750 = 18 carat = 75%

.585 = 14 carat = 58%

.375 = 9 carat = 37.5%

A gold item listed as .575 is 57.5% pure gold.

Its worked out thus:

24 carat gold is pure gold..

Therefore

.575 or 57.5% = 13.8 carat gold. Its real gold - not gold plated.