IVing IV, The Plastic Nickel

[Mark Kohut]

p. 294 So, they head to The Plastic Nickel on Sepulveda
http://en.wikipedia.org/wiki/Sepulveda_Boulevard

Plastic Nickel continues the coinage themes/tropes in this book:
Nixonhead 20s, Gold Standard, JFK what, half-dollars?, surely showing SOMEthing goin on herein re money, wealth,  America's monetary value(s)? tying in to the Silver-Gold stuff in AtD and somehow I would think to
all the paper inflationary worthless post-WW1 money in GR.......

All the presidents' heads on huge plastic five-cent pieces.........not nickel, the substance backing up that five-cent piece. 

uh, dare I quote 'plastics' from "The Graduate", 1967, nah, only if I say
it was 'in the air' then, I think. 

Other associations: 
http://bluestarpolicesupply.com/police-whistle-black-plastic-nickel-or-brass.html

Seems the phrase plastic nickel, can also apply to a size of a bag of weed, chronology of use unknown......

So, give me 100 words on money in Inherent Vice.