A three-dollar bag of heroin, ~1969 NYC, anyway. There were also the deuce and dime bags - self-explanatory.
A five-dollar bag of the goods was, for reasons I have never been able to comprehend, known as a "pound" bag, rarely a "nickel bag," such term being used mainly for weed.
Four and six dollar bags were called just that, fours and sixes.
The denomination one found might well depend on where in the city you were. For example, treys were common all over the LES, while deuces seemed to prevail in areas of the Bronx.
"You holding today, my man?"
"I got treys, how many you want?"
God's own medicine and no doubt about it. The previous definer who said it "sits alone atop the drug tree" was right on. If it were legalized in the US, property crimes would plummet.
Heroin is derived from opium and described as follows:
Someone who won't give up anything under interrogation.
Standing up to questioning.
Cop: Awright asshole, where'd you get that illegal substance
Guy: I dunno what that is or how it got there. Never seen it before.
Cop: Oh yeah? We're gonna lock up up and throw away the key if you don't tell us where you got that stuff.
Guy: I don't know NOTHIN' about it!
Dig it, you are a stand up guy!