Here's something courtesy of Greg Smith's Why I Left Goldman Sachs.
The 'Partner Laugh'
'This occurred when the trading floor was dead quiet and suddenly you heard some kiss-ass VP erupting into fits of laughter and slapping his knee in response to some joke the person by his desk was telling.
The longevity and high pitch of his laugh would tell you that the person by his desk was a partner. (A close relative to the Partner Laugh was the Custy Laugh: short for Customer Laugh. This sounded just as fake, but was reserved for sucking up to your biggest clients and usually was louder and built up at a more gradual pace than the Partner Laugh - only a trained ear could tell the difference).
The other way to pick a partner out of a lineup: they were always tanned - even in the winter months'.