《今日发现》解释称，这一做法也曾用来判断硬币是纯金的，还是用较便宜的金属镀金的。 。
Thee practice also once served to see whether coins were solid gold or just gold-plated over a cheaper metal, Today I Found Out explains.
《今日发现》解释称，这一做法也曾用来判断硬币是否是纯金，还是仅仅是用较便宜的金属镀金而成。
The practice also once served to see whether COINS were solid gold or just gold-plated over a cheaper metal, Today I Found Out explains.
起初这种在涂色中几乎不留线条的双层镀金属的工艺对他来说是全新的，而且技术性很强。
The double-layered and plated technique of leading Mr Denny’s glass, with the lines almost lost in the painting, was at first new to him, and correspondingly tricky.
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